No its not in a temporary folder. I was on cutting edge before/after the loss of local scores. I switched to latest after making this post to try to stop the hemorrhaging of local scores.
It certainly wasn't the only local score lost from that night. I suspect something was added that deletes local scores when it is unable to find the beatmap the score belongs to? If so it would make sense that scores are going missing and maps are being removed from collections when the game is unable to detect them (sometimes I have to F5 and reprocess beatmaps to detect like half my song folder).