Assuming this is a scam, how does it work? : Scams

A relative got this note on their car. (parked in the streets of San Francisco) Car looks ok but is older.

Somebody else (not Steve) answers the phone. Makes an offer, I think it was $500, They are hot to buy the car (while not certain which car it is and “get talked up to” $2000 in spite of a check engine light issue. This is all on the phone at this point. No inspection, They are up to something. Is it buying a car to use for porch pirating and never changing the title and then ditching it when it is no longer convenient? Or what?

Edit: the note is a copy. So they leave it on many cars, presumably.