Has this happened to anyone else?

So I haven't played this game since 2015 after my friend stopped playing, haven't given it any thought since he had no intention of picking the game back up. However, a co-worker at my new job piqued my interest again as he plays and wants to play with me. So I tried logging in, and lo and behold I've forgotten my password since I hadn't played in three years. I put in my username and tried to recover. Logged into my old email (that I also hadn't been using since the high school years) I found that I actually remembered my username wrong (sorry to whoever received an email for that). How I found my correct username you ask?

Well, it was attached to a ban notification...From April. No, not April 2015. April, April April, from 2018. So I sat scratching my head and wondered if Riot had a cock up and banned the wrong person. So I logged in my account and checked my match history (i actually wanted to see if anything happened to my precious skins, but there seemed to be no way to check), and to my surprise, I found a series of games played in April, and they were all wins (except one).

I knew I didn't play those matches and then suddenly forget about them because my sister's birthday was on the 22nd and I definitely wasn't playing league of legends at her birthday party full of 8yr olds. As well as the fact that I didn't recognize a lot of the items in the hero builds. Heck, I didn't even recognize one of the champions (must have been introduced within the 3 years gap).

The real question is this, how do I prove to Riot that I wasn't the one on the account during that string of games? Can they check the IP address of the games in question?

tl;dr : Acc banned, dindunuffin (wasn't me, dont even know what the ban is for since the email didn't say), how do i prove it?