It's been my opinion since you posted yesterday about it, that he was either left behind by someone who stopped there (abandoned) or he fell out of the car. Poor baby.
Maybe you'll get a response to your flyers but I'm guessing you've got yourself a new pup and seems to me like it's the best thing to happen to that little guy. congrats!!! if you need anything, let me know. I've got tons of extra stuff from my little guy and I'm always finding bargains. I'd be more then happy to help send you some things for your new family member.