Whatever Riot's doing to punish people who violate the Code, it's not working. Fortunately, Riot has yielded to popular demand and allowed loss forgiveness for promos and stricter penalties for ruining someone's promo series. Oh, wait...
So, the hardest thing is to prove that they rage quit and had no valid reason to leave whatsoever. Even if they're mad in chat, you can't really say with guarantee they didn't have some sort of real life emergency, and in fact it may be a real life emergency looming over them that led them to rage in chat.
I get it's frustrating, but AFKs are punished by Riot, and if you think that punishment doesn't work, I encourage you to wait, staring at the client, without talking in DMs for 20 minutes before each game.
I had AFKs in 3 games (placements), went 7/3...yea those 3 are with AFKs. Sad but true...
Normally I'd say bad luck, but since now is a sensitive period nearing season end all things can happen.
