I've lately become interested in the "Lazy Man's" tek...and the first thing I noticed was more than one person complaining that their naphtha VANISHES. My theory: the naphtha molecules are binding very nicely to molecular elements of the bark that stay ATTACHED to the bark (which, of course, can theoretically happen even with powdered bark). THAT could be where the naphtha is disappearing to.
I can think of two things to do:
1)Warm it (you say it didn't work so well).
2) Just add more naphtha and continue on. Eventually (as the heavy lye content breaks and loosens up the bark structure--even in powdered bark) that naphtha should free itself. Of course, when it does it can bring along a bunch of nasty fats, etc, that you had AVOIDED up until then.
My conclusion: It's probably a GOOD THING that the naphtha gets lost: It's bound to something that you DON'T WANT ANYHOW.
Just add more naphtha and continue on, is my best advice (from someone who never did a SINGLE EXTRACTION IN HIS LIFE--but who has done a lot of lab work and has had to think his way through things like this
)