There is lag, where it looks on your screen like it stuck, but when the server catches everyone up it decides it missed...
But also I've noticed something else: when someone seems to have stuck me but they've died as they did so (like maybe I ran them over as they stuck me
) then often the nade fizzles out. I've also noticed when I've got a nade off, but then got rocketed and killed, the nade rarely seems to explode. So I just wonder if there is some tolerance where the nade will "undo" if the thrower dies shortly after.