I need to contact facebook immediately?

[Alistair]

You're an adult, so he is not a child molester, he is a potential rapist. There is nothing you can do unless you saved the URL from his page on Facebook, but even then, you're wasting your time since he was probably a troll if he gave up the easily. If he does come back, then you can report him for harassment, but don't tell him that you're going to call the police on him this time.