"After encountering the boss I ran away (to see if I could find more loot)"
the consequences of cowardice and greed
I'm just kidding. The doors are supposed to lock you in there with the big bad, but they are apparently run by a malevolent AI that lets players out sometimes to see things no player was ever meant to see. Really wish I had had more time to polish up the final boss encounter as I think it's the game's weak spot but the clock just simply ran out! Appreciate your bug report and for taking the time to give us a play :)