HACKED AND BANNED

Its been years since ive used my account, and when i tried to log in, it says i have a different password, i tried the only passwords that i use, but no avail. i decided to change password and i was able to log in on the website. then i downloaded the game and when i logged in, i saw "PLAYER BANNED" this account has been permanently suspended. Please check the email address associated with your league of legends account for additional details.

i logged in on my email, but i cant see any information/details given to me by riot.

and i also checked my recent games, there is someone who used my account... the last time i played was back in 2015. can riot detect the ip address who hacked my account?

please help me riot.