I've ran into this same type "bug" when I got imprisoned at Moonrise Towers prison level. I've tried everything I can think of, none of these worked. It also won't let me travel to Balders Gate from here, says the character is not ready. I managed to get back to Camp to have someone resurrect him with Withers, but then I was stuck at Camp.

1. Go to the Main Camp
2. Kill and Revive Your Character
3. The Grease Bottle Trick
4. Shove the Bugged Character
5. Restart the Game
6. Kill/Revive Party Members
7. Try the “Leave Camp” Option
8. Ungroup the Team