I would just call it and see what happens. Worst case scenario is you hang up if you're uncomfortable.
I've had unlisted numbers show up on a reverse lookup so don't let that deter you necessarily.
Again, I think you should at least try to call him. I think if he was a scammer he would have backed off when you asked for a number. If you call him you're probably going to be able to tell if he's a shady guy or not.
Good luck!
Derek