This is an unfortunate situation, and I pray this little dog went to a good home, but a reputable breeder does not have to advertise their dogs on Craigslist or any other ad.
Their litters are usually spoken for before the puppies are even born. It is ignorant to meet someone and give them a dog unless you or someone you know knows the potential adopter. With that saids, if you don't know the person from Adam's house cat, then you need to check vet records, personal references and a home check. This doesn't always ensure the dog is going to a good home, but usually if a person is willing to wait for you to verify their info and then pay an adoption fee, then the chances are better for the dog.
Personally, with all the dogs needing homes, why are people still breeding dogs $$$??? 4951