22yo DS1 just found it under the dining room table. It doesn't belong to his GF, who was here are the time. It doesn't belong to me, I've only recently had my ears pieced and own exactly 2 pairs. DS2 AFAIK has never had a girlfriend in the house. No one else lives here.
It was found with the butterfly back in place, so hasn't fallen out, it's a small pearl stud.
So how did it get there?