are you sure about that?Pretty much positive. Maybe it's possible, but I don't recall destructible walls ever being mentioned in the forum, and never found any myself. If the Larians were going to go to the trouble of adding destructible walls, though, you would think they would figure into at least a couple prominent quests or easter eggs.
The game has multiple areas, cellars, dungeon levels, etc on different 'maps'. Usually it only displays what you are suppose to see at that location, but sometimes you can see monsters on screen or the mini-map from areas close to where you are. I ran into a glitch in a game once, and got this
screen shot of the map (30KB) showing several dungeons and sewers south of Rivertown, which normally are blacked out when not in each area.
Also, it is possible some areas were changed before release, leaving creatures stranded outside of the play area.