Check who used to own your place and who owns that lot now and see if any names line up.

I still receive occasional postcards from real estate mogul wannabes for a property out in Colorado (I'm in PA). The previous owners of our house moved to Colorado after they sold us their house, and I assume their name is linked to our address in some gray-market/online DB. Why they wouldn't just send purchase offers direct to the house in CO instead of what they think is the owner's primary address (ours) I don't know, but I'm sure they fire off thousands of these things and don't really care how many are accurate.