I was eating a burger alone, at a bench outside of a fast food restaurant. I was very stoned and daydreaming and something hit me: "Heroin!" It was the answer to a statement posed by a woman in my daydream.

The events in chronological order:
She said something along the lines of "...it's not like one of the more common drugs." I had to decide which domain she meant by "common": Common in the city or state or nation? I considered that there aren't any well-known drugs associated with this particular city or state, so she likely meant "nation". Even if there were some well-known drug asscociated with the city or state, it wouldn't be as familiar as the well-known drugs associated with the nation, and assuming the woman knows this too, she would be careful not to use "well-known drug" in such an ambiguous way. So I decided that she meant "common in the nation". Given that assumption, heroin was the first drug that came to mind in terms of common-ness on a national scale (and other context clues which I can't remember anymore), so that was my answer.

The events as they appeared to happen:
"Heroin!" Wait. Why did I say that? It's common in US. Why is that important? She was using an innuendo, so I probably had to infer the spatial domain of answers that she was referring to. She could have meant city or state, but there are no drugs that we would agree are "common" on those scales and she would try not to be ambiguous. So, she was saying something about "drugs". She was comparing some other drug to the implied "common drug". Oh and she was saying "...it's not like one of the more common drugs". Eureka! She meant "it's not like heroin"!

When the Eureka moment hit me at the end, I finally felt that I had understood what she meant. My answer seemed to come at the same moment as my understanding of her statement. It felt like I could suddenly see the entire chain of events all at once for the first time. It suddenly became unclear in which order the events actually happened. After the Eureka, it seemed like the chain of logic started with the question and ended with the answer, but I clearly remember that the chain of logic actually started with the answer and ended with the question.

My theory:
I assume that I did indeed experience the chain of logic in reverse initially, but that this experience must be somehow hidden when I'm sober. This is amazing because it implies that when we are trying to understand something we approach it in retro-causal order. In other words, we understand something in the present by asking "what caused this" over and over again, rather than starting with guesses of an initial state and asking "what does this cause" over and over again until we find the right one. I can offer two reasons why the former might be better in general when connecting logic:
1. Guessing a cause from an effect is much quicker than guessing a cause by picking causes at random and extrapolating until finding the right one. This is so because the former uses the cause to narrow down the space of effects that should searched, while the latter starts with no assumptions and picks a cause in a very large cause-space.
2. Any deduction about the past starts with an event in the present. So it would be compuationally economic to process that information first since it is already loaded into the neural buffers. For example, there's a cactus and smashed pot on the floor next to your friend. It must have broken when it hit the floor. Your friend must have dropped it. He's holding his hand in pain, so he must have pricked his hand on the cactus, and that's how this all began...
But if the friend recalls what happened, he'll explain that he was holding the cactus and got pricked, so he dropped it and it smashed on the floor. But this ordering of events is the reverse of the order in which you logically discovered them. We deduce past events in reverse-chronological order, so maybe we would understand a retelling of events better if it is given in reverse-chronological order.

So what does this imply about the brain? It implies that when we make predictions or conclusions, we start with the end result and justify our way backward to the initial cause, which implies that memories are stored in a sort of branching categorization scheme, with earlier memories on the farthest branches and recent memories closer to the trunk. In other words, something about the way memories are stored makes memories like safes within safes, with older memories "deeper" than newer memories, and with keys that require memory to be recalled and explained in retrocausal order. I imagine that a memory is stored in the brain like a long encrypted string of data that has to be decrypted by a sort of ordered factorization process. Furthermore, this normally happens so fast that we are only aware after the retro-causal explanation procedure is completed.

As I walked home I thought hard about this so that I wouldn't forget it, but I also had an additional revelation. My unfolding of logic for the answer "Heroin" started with the answer and worked back to the question. But then how did the answer get there to begin with? Ancient philosophers attributed these proto-thoughts to divine sources...Nah, there must be another explanation. I decided that there could be a part of the brain that bypasses causal logic to come up with the likely answer quickly (something like intuition), and then there's another part that fills in the logical explanatory gaps afterward.

Perhaps the ultimate irony is that this realization is made very difficult by the fact that every subsequent step deeper into the realization causes yet another time-reversal as we repeatedly try to explain retro-causal recollections. And so it can become very hard to remember the true order that perceptual events occurred in, or to see the whole picture of the fractal nature of meta-understanding.

Another interesting thing about this whole experience is that I spent so long trying to figure out the answer to a statement that was asked by a woman in my own head. I was surprised that my mind can subdivide itself so well. I imagine that there are many segmented minds which can be loaded with copies of kernels of consciousness so that these kernels can interact with each other from various angles, and this somehow acts as the machinery of self-interaction.

TL;DR:
The reality you perceive first is present reality. Therefore conclusions and inferences are derived in retro-causal fasion, i.e. by asking "what caused this" over and over until finding a final answer. When we get to the final answer (often the earliest relevant causal event) we have a Eureka moment where we are focused on the final answer and forget that we found it via a retrocausal tracing of logic. When we finally recall the event of understanding, we remember it in chronological order.
So, the experience of time in reverse was me suddenly noticing that every conclusion I make about the present requires me to think about events in reverse.

Hix this is fantastic!
You caught a glimpse of the subconscious mind(s) talking to themselves.

If I may break it down to what I understand when I read this.

(Drugs (common drugs (heroin)),(?)))

The mystery drug (?) is the answer to the initial question - "what is a drug that is not like the common drugs?"
The drug that instinctively came to mind to you was (Herion).
But heroin is not an uncommon drug, it is quite common at least in the zeitgeist of knowledge. It may not be so common by way of use.
So depending on the context, heroin can be in a superposition of being both common and uncommon relative to the statement.

"It (x) is not like one of the more common drugs (y)."

For heroin to be categorised as common, the category need be commonly known drugs. (Y)
For heroin to be categorised as uncommon, the category need be commonly used drugs. (X)

The superposition is due to the apparent vagueness of your friend-self.
Which, to those of us who accept the partitioned nature of our consciousness is not the most interesting aspect to your proposition.
Typically it is very difficult to be a fly on the wall to conversations of the different conscious "bubbles" within ourselves. You will speak directly to one, but that's about the only time you can sense the partition.
But, on this occasion it appears to me as though while buried headfirst in the present moment enjoyment of a super-stoned burger, for a split second you overheard a conversation happening behind your awareness that might not have been intended for you to hear. The stuff about the common drugs etc.
If I were a betting man I'd put my money on the notion that your partitioned self(s) were discussing the nature of compulsivity while watching you being engrossed in your burgerish delight. Perhaps they made an association between fast food and addiction.
And the perfect fit of the heroin superposition caused (hah) you to be stuck in the loop of cause-effect and see the mechanics as they are typically not observed.

Anyway that's my .02 (most likely wrong (and definitely nonsense)).

Thanks for your interpretation! Revisiting this experience though someone else's eyes was insightful, especially since the realization has mostly faded.

Your level of stonedness appears to have been over 9000. I went that high once , in a neural safe far far away. I haven't smoked weed since.. the intense mirroring pattern that happens sends me into what I would describe as some kind of slow motion epileptic fit, and what you wrote above is a good example of what it looks like.

At first you are filled with disbelief,, what powers of observation!.. but coming away from it after with always the same thing: nothing. And it's so hard to remember what that nothing was exactly, because the words and meanings and intonations we use to try and reproduce it.. fail. You can write it down, even take the extra time to purify it, crystalize it in your mind in so many words. You can write: 'We are all we are', and sink into sleep with utmost sense of accomplishment, only to go back and read the most simplest given in the history of all that was never ever fu88ing written.

Anyway, enjoyed reading.

This is an amazing description. As you say, it's not that the words don't make sense, it's that their meaning is completely trivial. A very shallow statement was somehow supposed to represent something very deep. How nihilistic to think that meaning and depth are so subjective.