Of course if the other team notices it. I don't check teams constantly and while being in action in the middle of a cw, I don't notice when someone lags out or disconnects. This doesn't make me less of a fair player, I'm just concentrated on the game. I'd just expect the other team to notice when their player has dc or laged out and say so, I'd have no problem to drop.
Exactly, nothing to add there, it's the dropping teams responsibility to get attention to it. However if the team with more players then refuses to drop one, then that is another point to talk about.