I wouldn't know how to do it if there was a way, someone else is going to have to step in for you there. That is the place I mentioned that triggers Nimhe though. Shady is supposed to have that Argus, she has one every day even after you buy it from that point going forward even though you only need one. So it looks to me like it's bugged.
I've had it happen that things that were supposed to trigger took a few days but I'm guessing it's been a while already for you. Try buying something, anything. See if the inventory updates, just a wild shot.
Edit: Also, the comment below is correct. You need to talk to the barkeeper but I'm thinking you already did that as well. Worth a try though.