[1.0] Unknown tunnels staircase disappearance

[serll]

I beat the assassin lord, opened a chest, beat the party that popped out and now I find that the exit has vanished. I have the save backed up on my hard drive if necessary.

[Velorien]

This has happened to me before as well.

Fortunately, you can use the Rod of Recall to get out, and the quest will still count as complete.