Exit the game completely, then start it again and reload your save. Hopefully you have not re-saved the game outside that room, and deleted/overwritten the previous save...
There is a possible bug a few people have encountered in the PC version; sometimes when quick saving/loading indoors ladders can get removed or doorways sealed. If you notice this right away, then exiting the game, restarting and reloading the save should work normally, but if you don't notice and save again it gets written into the save file.
Missing ladders in dungeon...stuck inside!There was also a possible problem in the original US Xbox release (since patched) that could alter your character's location when loading a save that had been over-written (exiting back to the dashboard and starting the game again would fix the problem, and always creating new saves would avoid it).
