Yeah soemtimes the stats system is a bit funky. I ocasionaly got wins when I quited a game, sometime I won but didnt get the win. I'm prety sure it's a knowed issue and is probably cause by alloy sicne i started noticing it about at the same time.

It happens when your playing strangers, i would like to think that it doesnt happen often but it seems to be a common complaint apparently. You also have to remember, the game crashes on some players some times causing their game to shut down and dropping out of the game as a result. (I recall the mini-dump error) Personally i play with a group of friends and other players that dont quit out on each other when get a slight hint that they might lose.