If you still have the save before that point, you can zip it and email it to me (raze@larian.com) to take a look at.
The 'secret' passages I was referring to don't need to be revealed, they are just 3 corridors through a wall section that are not obvious if you don't look closely. When you get to a certain part of the room the imp there, named Taxlehix, gets a cutscene conversation, and challenges you to find the correct path (2 have minor traps).
At that point in the game you can trade with the imp and learn a couple skills (pickpocket, lockpick, sneak, poison), but if you can get past the cutscene you wouldn't be missing very much with him being stuck in the wall.