It's so annoying, and I hope you don't lose out financially, Osc.
Over here, if you don't exchange details at the time, it's an offence not to report it to the police, even if it's in a public supermarket car-park.
You do have to watch it in car-parks - some people just drive into bays and leave their front-wheels at an angle; when they then drive out, if they don't watch it, they swing wide "too early" and can swipe a vehicle parked alongside.
This actually happened to me on Monday, lady in a Smartcar (of all things) clipped my rear wheel arch while she was reversing out of the next bay. I was actually standing next to her waiting to offload my shopping into my boot once she'd gone, so she couldn't exactly get away with it!

Anyway, she did stop; I inspected both cars - very low speed collision, no visible damage done to either vehicle, so we left it at that .....