Cell phones with picture taking capabilities can help too if you do not have a disposable. Take a picture of the scene, the license plate of the offending party, close up of paint on their door, close up of paint that is no longer on your door (i.e. the ding, scratch, dent), close up of offending party as they approach you, close up of their insurance card & license (just hope they are not an 'illegal'), and hopefully a wide shot of you with the 'big check' (think Happy Gilmore) that they pay you to not report it to their insurance.