RV Broker came to our house

We are brand spankin' new Class C owners. We bought our coach from a dealer a week before we flew to Alaska for a two week vacation. While we were gone, a note was left on our front door asking if we would be interested in selling. Our son, who was house-sitting, retrieved the note (with no name) and gave us the phone number. DH "googled" the number and it comes up associated with various RV sales publications. He called the number, got voicemail, but chose not to leave a message till we research further. Any ideas on how he knew we just bought an RV, how he tracked us down, etc? We live on a dead end cul-de-sac and only homeowners drive back there. Any thoughts? Help!!!! Thanks!