I wonder if this is just a matter of my memory being odd, but I could swear we said “to prom” interchangeably with “to the prom” back in the early-to-mid-90s. As in, “who are you taking to prom”? At least it does not sound the least bit odd to my ears, and I haven’t talked with anyone or heard about prom probably in about twenty years.
Like here’s a post from 2000 on this board, and it uses “to prom”:
ETA: Oh, I see you said “in the last 25 years that the article disappeared.” Well, my sense of time is warped, I see, so my experience would actually track with your sentence.
ETA: OK, better cite. This is from 1926:
“Many of our girls are going to prom …”
“For the thirteenth man that I asked to Prom […] Oh, the thirteenth man that I asked to Prom […]”