I've had a similar situation back in college...But I'll skip this story and get to my actual point. When I was in this "similar situation" I still had stand up aspirations and it was one of the things that shook me out of it. That someone would have a similar story that they would use as a bit and me, not knowing about it, would do the same bit and be called a hack.
Yours is dog poop, and mine is weed but the nosey eldely person is the same, so it's not quite an exact tale, but almost everything else falls into place. Since I never took it up seriously, I'll ask you....Does it ever worry you that something you do could be referenced to another comedian and despite your not knowing about it, caould it come back and take the poop on your career.