Griefing?

I got a team where we did fine early game, and then late game we got stomped. The team kept failing to focus squishies, even though I (amumu) was gettign at least 3-4 people per ult, and usually their entire backline. But anyway, it's the last team fight, no nexus towers, and 5 v 5. The enemies rush in head first, and their adc and ap mid are instantly destroyed by my ult and everyone else...only problem was, it was a 3 v 5, our ap mid and tank top had ran into the jungle for no reason and ran to the enemy turrets to ensure our loss...what pisses me off, is these two probably got away with no punishment after intentionally losing a game. We managed to turn a 3v 5 into a 3v 3, we could have aced, and probably won (late game death timers), but these two ***holes ruined the game for everyone.