I just had multiple accounts "banned" by having the passwords changed with no email history of the password changed and the username/password recovery not working at all. Even accounts I had not logged on in over a year were all simultaneously changed password.
I am guessing Riot for whatever reason initiated some kind of password reset for security reasons. Why they did this instead of locking the accounts for security purposes I have no idea.
I guess it is technically possible I got hacked, but not all my accounts and none of my other info was compromised and my accounts have different emails and passwords.
Is this a known thing where Riot resets your password so you can't login? I have never heard of this up until now.
Apparently after doing some searching, I can find at least one example of this happening to another user, but it seems to be incredibly rare:
So no, I was not actually "hacked" this is just apparently something Riot does when they don't want to let you know the account is lockedor banned and they just want you to be paranoid that you are keylogged or something.