Maybe I was thinking of returning to the castle to lockpick stuff left on the walls, or something.
I didn't have any problems with this quest; the first time I talked to Ben he accepted something from my inventory by the time I got to him (looting on the way). If I have time later I'll check this out more carefully.
Maybe the wife/girlfriend of the 'drunk' runs after him when he pickpockets you, so that is why you don't meet her if you meet him first. Practically, her only purpose is to warn you about getting pickpocketed, so she isn't needed if you have already been robbed by the supposed drunk.
