I had to go through the account recovery on my Facebook account once and the proof they demanded was that I match a bunch of pictures of friends to their names. I think it took 3 tries over multiple days to actually get it unlocked because it turns out I such really remember a lot of the people I met 20 years ago and friended on Facebook.

I don’t recall why I had to go through this song and dance. Very plausibly the account was still associated with an old school address that I could no longer access. So yeah, account recovery is hard. How do you prove someone owns an account when they’ve lost the things they are supposed to use to prove ownership?