"Picked up at a thrift shop"... Is there something you'd like to tell the class, Mr. Morichika? (Though admittedly, he's not the only second-hand store in Gensokyo; she could have bought it from Marisa's dad. Is that better or worse?)
I think the other obvious joke here is something like, "Oh, yeah, the strapless dildo crossed the border into fantasy so quickly because dildo-obsessed lesbians was mostly a fantasy to start with," but that's a little mean. Plenty of non-forgotten objects do make it into Gensokyo — Rinnosuke has stocked items like iPods and handheld game consoles without too much time lag.