On my daily driver, a Ford Focus ST, there's a little ding on the passenger side. For that one, it's possible that somebody in a parking garage just didn't notice when they opened their door or something like that.
But on the driver's side, there's a 20cm long depression with a scratch-line where the paint has come off. That was somebody backing into my car with the corner of their back bumper. No way they didn't realize that.
Anyway... nobody ever left a note. And this happened a month after I changed the insurance of that car to the kind where my own damages aren't covered. :-(