I experienced the same, and as far as I know this seems to be a design flaw of this room.

There is a "puzzle" in this room to open a backdoor by using the missing rune on the pedestal with an empty slot and that rune is carried by one of the druid's in the center room. The problem is that if all of your party are inside the locked room and you haven't stolen the rune then you cannot escape (as far as I know).