Im with Dan. I can hide, and he can stand still. If they then turn up, I can use my powers to unmask them, and we can find out who they are. Plus, we can find out the type of van, and its numberplate. Could we buy some sort of tracking device? If so, attach that to the van. If not, then bugger :-P

If not, then we still have some idea of who they are, and we can go to that John dude and find out about them.