Songs I downloaded yesterday from CDs using Music App have disappeared

The music I downloaded from my CDs yesterday using Music.app are gone today. Missing. Poof. The entries for them are still in music.app, but at least half (maybe more) of what I copied to my computer disappeared. I asked AI Gemini where they might be. Gemini told me how to find them. I followed Gemini's directions, but the songs aren't there. A few songs from a few albums are still present but most have simply disappeared. Where might I find all that music?

Is there a good alternative to Music.App, one with very similar functionality? I'd like to broadcast music to Google speaker groups.

I do not subscribe to Apple Music, Google Music, Spotify, or anything else.