Banned while I sleep? Using 3rd party?

So if some one can explain to me why I was banned for using third party application.

1. I'm assuming that means cheats which I do not have.
2. This ban occurred when I was sleeping.
3. I haven't played league in 3 months due to hand injury.
4. Two days prior I was emailing riot support to get my password back (some kid hacked my account apparently) which I assumed something would be done about or at least none of his transgressions would affect me.

Now today I wake up to a email telling me I'm permanently banned? Been playing this game since season 3, I know the rules. I've invested decent amount of money into this game, now I'm banned permanently for something I didn't do? I do not cheat, I do not trash others, I do not afk.