Loss Prevented

I would just like to know why there isn't a loss prevented in cases where there is no way you're able to win a game. For example, a game I just finished playing I was matched with a teammate that raged in champion select because Olaf was banned and that was his main. When the game started he walked into the enemy towers giving everyone kills as soon as he could. We eventually lost due to the fact that he had spread the kills evenly among the enemy team and we couldn't do anything even though we'd won every lane. After the game I checked his profile, and he doesn't even play Olaf, and his match history shows that he trolls every ranked game yet he's silver 1. Secondly, I also played a game a while ago where two of my teammates were AFK. Just wondering why there isn't a working system that prevents these losses, or at least removes these toxic people from the game even though there is said to be a working system this guy is able to troll many games in a row.