Thanks everyone for looking! Keeping my fingers crossed!
(My collection of pins, we've used to make a shadow-box display. But she likes to wear hers on the tote bag she carries at conventions. This pin slipped off during one of the seminars, we went back and searched a good radius around her chair, but no dice. We also wrote on the lost/found/wanted whiteboards, and posted in the IPMS Nats Facebook group, but no luck. It probably got swept up by the cleaning crew.)