Did this really just happen?

We have a 3rd pick and a 4th pick, our 3rd pick picks Ashe, and our 4th pick decides to lock Cait right after saying "I'm better than him". So at this point, I'm still fine with his messed up attitude, and decide to play. BUT, this guy decides to go afk for 15 MINUTES, comes back and says "lets speed this up" and dies while walking up to the enemy. Afterwards says "I told you i wasn't going to play" and proceeds to afk till the end, therefore we lose. (PS. This is diamond)

Can I send in a support ticket to get the 15 lp I lost back? This guy even admits to his wrongdoings inside the game, therefore we have proof.