Some of the ones from good breeders, the breeder might actually replace the dog, depending on the contract signed. And the majority of "pet quality" puppies from good breeders are about $1000 (at least they were last time I looked into it), so even though it's an expensive dog... it's not as much as a lot of people think.
Anyway, I do feel bad for the cat, but it's true that there's not that much you can do if the cat is definitely already dead. It's not true that no cat has a tag/collar--my family's cat does--but it is true that most people don't put them on their cats. The only other thing would be if it were microchipped, and that's less common for cats than for dogs and would have required taking a cat corpse to a vet or humane society to check... and I don't feel like I'd do that either.
Definitely would suck worse to hit a kid's dog in front of the kid, though.