On Facebook, where did all of my photos go?

Facebook is often glitchy for me, especially photos. Maybe they’ll be there if you check back later (sorry, not actually very helpful).

If they don’t return and re-appear. Contact FB, they have been known to drop things off their servers.
Like @syz said they are glitchy. It is not a “mission critical” operation for cloud storage of photos.

My account did that for awhile and like they said, the next day or two later it’s fine.