If he was there, why was he there? To take a peek at how Voldemort finished off the Potters - a reward from the Dark Lord to him for obtaining the prophecy? I don't think so. If he was there, why would he have to be under the invisibility cloak any way? He was in cahoots with Voldemort then wasn't he? And if he was there with his master, why didn't he finish off Harry?