That does sound a little suspicious. I mean, even if they did work with/for Petfinder, they shouldn't have mentioned it if they were truely looking for a pet themselves...just doesn't sound right. Your babies are definitely NOT rescues. Maybe petfinder is trying to catch people who are BYB or puppy mill owners..you know..fighting crime.
I don't know.. Just sounds weird. Maybe next time, you should drill them, talk to them a little longer, get a callback number and try to see where they're really coming from....