Magically, the dress reappeared online and, fatefully enough, the only one left happened to be my size.
It's very short, it's very sequined, and it came in right before my last sorority formal, so I decided to wear it instead of waiting another two months (and covering it up in a drab graduation gown). It was a good choice; wearing sequins makes dancing so much more fun.
(left, a "mom, does this look ok?" snapshot. right, a pre-party picture.)