Weird Ban

In my ranked games i hardly even use the chat at all, and rather prefer to just mute all the other players because they flame at me whenever i play Singed. I just came home the other day to find that upon logging into my account, it says this account has been permanently suspended. This ban is really weird, because i have checked the associated email, and i see no riot games email explaining to me why i got banned. Also, this has been my 1st offense in 2 years, with the last one being leaving games too often when i was just starting the game. Can i really get perma-banned from a 1st offense in over 2 years? Wouldn't i receive a warning 1st, or at least a timed suspension? This really is baffling because it came up from nowhere, and no one is explaining the reason for it to me. I really am in need of guidance.

Edit: I just remember starting a week or two ago, every time i finished a game or when i was just randomly in the client it stated that account was logged in elsewhere, when i'm sure i hadn't told anyone my account credentials. I feel like maybe my account being compromised may have something to do with it? Cuz i feel some games in my match history i never recall playing at all