Is there a permanent invis bug with Vamp Ultimate?

leepalmer95

So me and my two friends were on the big bridge, one of them had to do something so as we was waiting two vet 8's come. We managed to kill them, two mins later they came again, killed them again, and again a 3rd time. The next time they came one of them used to Vamp ult that made him invis. Fair enough, after it ran out he didn't appear, he was still attacking me for over 2 mins before his friend turned up again and then they managed to kill me, how was he invisable for that long, i also swear he used the vamp ultimate twice in a run as well.