then I might have a bug of some sort maybe ? Because I opened every chests of this cave the first time I went there; I just rechecked and i'm pretty sure they were all opened but no sign of this crystal. If it was supposed to be in the big chest in the center of a room then this chest is allready umpty for me ^^'.
Should I do the game all over again ? I'm not sure I would love that...
I might be missing something but I cant tell what if I do ^^'