EDIT: Realized my stupidity, the line is most likely where the glass during manufacture has been joined, thus not cracked

Is that a crack where the chamber narrows? :'(
I think it was because the pipe was so cold that the change in temperature from the jet lighter expanded the top half of the glass chamber while the bottom half remained cool causing the glass to crack..

It's hard to say for me because of the quality of the picture but using a tri-flame torch isn't the smartest idea because it will heat up the glass too much instead of the diffusor. Go into a dark room, turn on the lighter and put the flame into the diffusor: You'll see that the diffusor won't be able to "take in" the whole flame, you'll see the flame hitting the glass way too much. But if you use a one flame lighter keeping it straight down into the diffusor I don't think that you can crack the GVG, at least not a healthy one.
If there has been a manufacturing error the GVG will at some point crack if you use it extensively but this should be covered by the VG life time warrancy.
Just send them an Email and ask them for their advice, if you're lucky you'll get a free replacement.

PS: Clean your GVG, it looks filthy! ;p

Clean your pipe with some acetone so you can see more clearly what its condition is. If the glass did really crack from the heat, contact the seller or manufacturer. The device is intended to be heated in normal use and should be able to take the heat without cracking. Good quality borosilicate glassware should be able to handle some amount of heat shock. If yours didn't it must be a production quality issue and you should be eligible for a replacement or a refund. Obviously, if you have to send it back, clean all traces of DMT from the pipe. Use acetone or alcohol first, then soak overnight in strong bleach.

The instructions that came with my GVG say not to use a torch lighter.

I dont see any fracture but its hard to see since its so dirty.

Def clean that GVG. You`ll get cleaner hits, and lose less product (condensation piles on condensation).

Regarding torch lighter, ive used the torch lighter with the gvg for years and never had a problem. I think they added as a disclaimer/warning because some people were going totally overboard with the torch lighter pointing directly at the glass. the flame should be pointed towards the ceramic in the center opening, and you can keep it a bit farther away and bring closer gradually, moving back when the vapor starts appearing. Once you get the hang of it, its very efficient and not dangerous in terms of breaking the GVG from heat.