Not likely that anything happened. The logistics make it VERY difficult. He most likely smelled her and followed her home (most intact male dogs can smell a bitch in heat up to two miles away), but would have encountered difficulty in actually mating. The anatomy has to fit for successful mating to occur and in this case I'd be surprised. You can consult your vet reguarding abortion therapies. There are some options to abort a pregnancy with certain drugs, but most have a pretty long list of side effects. I would advise talking to your vet, and depending on what they say probably waiting a couple weeks to see if signs of pregnancy develope. Cant guarantee anything, but I'd be surprised if she got into "trouble". Good luck! ~D