Riot! There is a bug that wouldn't let my brother log into his account! Please help! ASAP!

Riot, My brother's account is not letting him log in. I don't know why he can't. He doesn't know his email, so he can't change his password. We were playing and all of a sudden he can't log in after the weekend. It says the username/password is wrong for no reason. His ign is : YATRICKHA
It would be great if you can fix this! We were grinding! Getting him to gold! It would be sad if he can't get it back because all that money is lost! All that hard work I put into earning the money to gift my brother the skins. Please help! ASAP! Thank you for your time!