Sounds 100% dodgy to me, he doesn't want to meet at his house? Fine, I sometimes don't like that either, my garage has a vintage scooter and motorbike in it, so I meet at my mothers, he will have friends or family locally, or, could have people be "with" him. Let it go.
Or, take somebody with you to the car park, bop him, and take the bike, that'll teach him.