Dogs have really good noses and the difference of air pressure between the store and outside could make a scent move far faster than you'd think. I'd see scent as far more plausible than psychic powers at least.
I mentioned this in another comment, but one explanation could be that the person in the car started to smell different due to seeing his friend. Pheromones from subtle excitement.
This discussion got me thinking about all the pheromones we emit, but can't really sense anymore. I wonder what sort of information are we constantly spreading that essentially no one is picking up. Or maybe we are, but only on a very subconscious level.
