I did get the note and the guy in the store had me go to the Mayor's assistant and have her order something. I have gone through all the steps that you have. The one difference is that I did dig up something in the middle of the stone circle and it was a note it is it's gear information. I think I was told to wait for something in order to use it, but I can't remember and nothing has happened.
I've tried to give this note to every town person and every person at the stores - the museum guy, the guy that you buy stuff from in the store, the guy you sell stuff to in the store the people in the bank the mayor's assistant and the clothing store clerk. I also tried giving the notes to the mayor' child and every merchant that shows up to sell something, and no one takes it.
You mentioned a riddle - I can't remember what it was, if it's about digging up something in the stone circle, I have done that and have the not that says gear information.