So riot what are you going to do about the AFK in ranked

First of all I win 7/10 games in ranked and I get put in bronze 5. Ok that's fine -.- well then I decide to play a game (Ranked game) everything great I get super feed (30/6/10) with ahri and then just when we are about to teamfight MF suicide and afk, She never came back and we were about to win and instead of wining like we deserved the enemy baron and push down til nexus. Then I lost 17 points from losing. SO RIOT ! ! tell me is that fair? with the current extreme unbalance in league how are we supposed to win a fight like this. It's 5v5 ranked not 4v5 or 3v3 or anything. Please find someway to make this fair when ally afk .