I had a Mercedes scraped on door and wing, in a Waitrose carpark, but when I returned, a kind soul who had witnessed it and watched him drive away had left me a note with the culprit's reg. number and his own phone number so I was able to successfully persue the matter.
Incidentally, I wish all car parks would use the herringbone layout as used in the US. It makes parking easier and really costs no more space because the aills (can't spell it!) can be narrower