Loss Prevention

Ranked Game, Rumble feeds 3 deaths (And when I say feed, I mean just walk up to enemy and turret and die on purpose) and afks, at lvl3. Yi gives up and dances top. Taric and Jinx start to get focused and feed, begin to blame and flame others once Rumble was gone they had to turn on someone else. Needless to say, we got stomped. I ended up 3/3/1, 3 out of team's 4 kills. Why didn't we get a loss prevention? It just seems so rediculously unfair to me.