sapphire gem 6th floor

I have a "small problem" and that is an understatement..

i used the sapphire gem to open the door (which led to the place where you have to put in the memory chip) before putting the gem in the opening (the three painting or something like that) in the room where the prototype of the ageless clock stand...
now i can't finish the game.. and i can't find a save game to undo this...

who has an sollution... or knows where the savegame is and how to manipulate this so i can do redo this part of the game...


thanks in advance
Marcel