Thieves Underground and the Tarant Sewers map.

After hours spent trying to find how to join the Thieves Underground, I happened upon Thaddeus Mynor on the east end of town almost by mistake. He told me all I had to do to prove myself was steal the map to the Tarant sewers. Sounded easy enough to me.

The problem is, I had already stolen the map to the sewers long before ever even hearing about the Thieves Underground. Now when I talk to Thaddeus with the map in my inventory, all he says is "You've returned", and the only dialogue option I'm given is "I must be off".

I even went and planted the map in the safe in City Hall where I originally found it before going to talk to Thaddeus. I retrieved it only after talking to him and making sure the job was written down in my notebook. Still no luck, though.

What could possibly be wrong, and what can be done to remedy the problem? Any ideas?

I would appreciate any help.
Thanks

 

That's, I think, the bug. Not following the logical consequence of what must to happen leads to this.

 

Yep. You can't join 'em now. All you can do is to restart the game and go with the same character again.

 

Bah, oh well. I'll go steal everything for myself anyway.

Thanks guys.