They Left Evidence at the Scene
Someone crashed into this person’s mailbox and didn’t leave a note with their name and number. This would have been the courteous thing to do so that they could talk with the owner and offer to pay for a replacement. But instead they left the scene and thought they got away with their crime.
However, they didn’t realize that they left their front license plate attached to the mailbox. This undoubtedly made it easier for the mailbox owner and the cops to track down the hit and run driver.