Getting put on Low priority Queue when you deal with a troll

So i queued up for a game of ranked with my buddy Noochy booch and we get a troll sona. so i decide after losing tower to afk at second tower and farm. Sona joins me and stands still and after dying when im no where near the person states "i saved you" after the game finally ends i get put in this low priority queue, how does this make sense i still played the game some afk system. And what makes it worse i waited 20 min right now to joing another game and it resets? cool.