[Radek]

If I understand well, you have left the Boogre Prison through the backdoor and occured in a small area without connection to the rest of the wilderness. You have found Doshi Gin there but you haven't found any exit.
Well, no exit exists. Return to the Boogre Prison and use the second exit from the "worm stick" room. The second exit leads to the regular exit from the dungeon.
Another possibilities are the Vanish spell and the Call of Home spell.