I think lemmynsfw did something in their end. My lemmynsfw account was logged out from all apps as well.

Mine vanished too and as it was a throwaway, I didn’t save the password in my password manager. I can’t remember it so I guess it’s thrown away now lol

It happens with various servers, often after an upgrade etc. I’ve had similar things happen with lemmy.world as they were experiencing issues and then updating

Mine vanished as well, but after I added it back it now works fine again.

I’ve had to readd multiple profiles multiple times, but not lately

Happened to me a while ago too. Actually didn’t notice that it was only removed from the app and thought it was gone altogether, so I was real stressed, but it didn’t happen since.