*******SPOILER*********
Thanks guys! I wonder if I didn't pick it up and then lose it during the lich fight... two of my party got "imprisoned" and I had to rest to learn freedom and then free them; I wonder if maybe they dropped it when imprisoned, I didn't pick it up, and then it got cleaned out of the crypt while I was sleeping in my pocket plane.
In any case, after searching diligently where you guys suggested and finding nothing (again, I probably lost it somehow before I needed it), I couldn't bear to go all the way back and play the whole level again so I resorted to figuring out how to set the debug switch to enable the console, and did a CLUAConsole:CreateItem("PLOT04F")... that did the trick.
I was a little jaded, because somehow I lost one of the gems on the level above and had spent four hours replaying that one from my save point in order to find them... wasn't about to do that again. I'll try not to resort to that again, although I must say I felt rather *powerful* at the console window!
Thx!