It was Matsuricon 2018. I've mentioned this in a previous post, but that con had an unusual twist: a Republican fundraising dinner was scheduled at the same time, in the same convention center. I am fairly certain that the concerned lady in question came from there and somehow found herself surrounded by crazy costumes. She did, in fact, pick me out of a crowd (probably because I wasn't cosplaying at the time and looked "normal") to ask me what the hell was going on.