They may have been casing your neighborhood for burglary targets.
Was it the middle of the day during regular business hours?
I thought there was another thread about this only the visitor asked whether the door-answerer’s car was for sale.
Obviously, you should have told them, “Oh, you’re looking for Cicero, the spy. He lives two doors down the street.”
(And yes, I know I’m replying to a zombie thread, but I couldn’t resist. :D)