I'm just curious what kind of program they have that goes through banning accounts that are inactive for 'malicious 3rd party programs'. I played for fun, not for competition. Even though I haven't played in awhile, I put a lot of time and money into my account and I'm very disturbed to receive an email claiming I was cheating.
You played a game 4 days ago. If you don't recognize it, then someone probably hacked into your account and has scripts on their PC.
I'd strongly suggest submitting a ticket and asking what's up. They also recently did a ban wave for potentially detected scripts from what I understand, which will usually include a mild chunk of people that didn't cheat but something installed on their computers caused a flag to pop up for the game's detection system and so they got slapped along with the actual cheaters.
https://support.riotgames.com/hc/requests/new
Make sure to select “I have a question About League of Legends/Riot Games” and category “Games and Features > General Questions”.
hopefully you were only one of the few that got caught by a false positive, also you might want to try doing a repair on your client to make sure it's fully up to date and has what it needs for whatever error you were getting when you tried to play.
good luck!
