Lost (almost) all FACES

I just transferred all my old iPhoto shots (>9,000 photos) to Lightroom CC a few months ago. Loved the transparent folder organization, the GPS map, et al. The whole system/set-up. I also meticulously went through and "named" 13 diff people with the face-recog feature. (I also noticed that they showed up as tags/labels.) Well, when I just by chance clicked on "People" today, all the face names had disappeared, except those of my own face! (It seemed to have retained all 700+ of those.) Panic time—as I considered, "Do I grab some backup catalog and see if if it has all this info?" But no, I spent half the day re-entering all the names, and then immediately backing up the Lightroom catalog. Odd that it saved only the photo names that were of me. ODDER STILL, the unknown faces it found were ALL the very frames I had already named, even odd out-of-focus or almost-outside-the-pictute faces that I'd DRAWN myself. Lightroom also did not display the multitude of strangers I'd already X'ed out. In sum, it seemed to rememeber everything but the names/tags themselves. Any help here?

I did upgrade to MacOS Catalina since the last time I checked the "face" feature, but I doubt it could be that?

A final related question: are these face "tags" saved to the actual photo files as metadata, or are they just stored in the Lightroom catalog? (I gotta suspect, even hope for, the latter.)