The files are still there. I can find my assets and my maps and whatever else there might be in Finder, but not inside Unreal Engine’s content browser. Through file > recent I saw a missing level, but opening it errors out with:
Failed to open map file. This is most likely because the map was saved with a newer version of the engine.
I have backups, but I don’t want to roll back a lot of work on my personal project. It would also be nice to know how or why this happened, as I haven’t changed versions. Lots of hours of googling frustration later, I’m hoping this can be solved.