If there is no damage on the car and he has no texts etc from anyone connected to you then just say he followed you home and is trying his luck.

Sounds like he's just trying to pull a fast one, probably took the bumper off the car and reversed it into a post thinking he's onto money. Next you will find he'd try claim whiplash. Ask him what proof he has that it was the young lad that ran into him and why its taking him so long to inform his insurance.