In Raedirc's Keep with my lvl 3 rogueless so far party I came across a number of locked doors that required 8 Mechanics to unlock. I also found a priest Nedmar who promised me a key to open those doors. I got the key from him and went downstairs into the main corridor with a pair of big gates. The key opened the first gate and then - poof it disappeared forever. As a result I wasn't able to open the second pair of gates, neither the backdoor in the chanters room or however it was called, the original intended target for the key. I ran around the entire area searching for alternative routes but couldn't find any. I saw a suspicious wall that was an obvious secret passage but none of my characters were able to spot it. But I was effectively stuck, unable to complete the area.

 

The workaround I've found was to give one of my characters the required skill to pick the door through the console and then revert it back to the original state, but it feels cheap.

 

Since I've found a way out, I'm posting this more to inform others and/or staff about this quite annoying issue.

_{I cant even get to nedmar i have noone with mechanics 4.}

Happened to me too.  Can't get through the final door, key disappeared.    Guess I'll be forced to cheat too.

There's another way into the room through the temple bit, if you sneak there's a little pink/purple thing that appears on the wall in the room next door, then a secret door opens. So you don't actually need to do the main door.