Rex the Wonderdog struck by a car

I had just taken possesion of the car i just bought, and was taking it to my 'rents' house(across the street) to store until it's registered and insured. The Dog jumped the fence, and refused to come into either yard, so i left a gate open for him, and i went back to my house. about an hour later, i heard a car drive by very quickly, i heard a thump, and i heard my dog yelp. I ran out, the car had sped off, and the dog ran into the yard, and was barking angrily in the direction of the the car had driven. The dog seems fine. he is not favoring a leg, i brought him, and i gave him a rub-down looking for tender spots. he didn't wince or growl, so it looks like he's ok. The odd thing is, everytime a car goes by on the street, he growls. I think he wants to go another round with that car. He's a tough dog, remember when he jumped from the moving car at 40mph? It's hard for me not to baby him, but still, it is his own fault he was out there. oh well, i hope he doesn't have anything wrong with him tomorrow