If you saw just a tiny bit earlier, I recently 
had this problem with a stuck sketch of mine. As 
in, it wasn't stuck like sketches are usually 
stuck. . . But more as if it was practically part 
of the cel! ~_~  Which sounds like where you're 
at right now.

The only thing I was able to do was a combination 
of the freezer trick and removing it with water. 
But I can note that were you're saying the water 
seems to be removing the lines as well. . . To 
keep the lines on mine, I couldn't just pull the 
sketch free - I had to carefully scrape it off 
the back of the cel with a knife. (On the plus 
side, that black backlighting paint is tough 
stuff and easily stood up to the scraping.) As 
you're doing this, you can't pull so hard that 
you wind up streching or tearing the paper as you 
go either. . . o_0;;  It's not easy.

Good luck!

Me. . . I'm off to try the freezer trick on some 
only lightly stuck sketches now. . .

Many Sharp Smiles,
--Drac