Hello,
I think some people here need to remember that a customer coming into a shop with the potential to buy something, should not be treated badly. Even if the customer is problematic, the retailer should do their very best to be both professional and polite.
If the shop values it's reputation and the potential custom, then it may offer a "goodwill gesture", but obviously without admitting any liability etc.
Personally, I would write a letter to the owner or manager, as Mr. Burgess has suggested above. Yes, it may help the shop in dealing with the staff member, but it may also draw some form of gesture from the store. I actually think it's appropriate, given what appears to have happened.
As for Poppy123, I believe that every person is entitled to be treated with dignity and respect, but unfortunitely in the wonderful world of dealing with customers, that doesn't always happen. Employers expect employees to have a thick skin and act professionally, even when dealing with a problematic customer. You could perhaps refuse to deal with a particularly problematic customer (in which case, probably best to try and do it in agreement with your superior and ideally, without even making the customer aware that you've removed yourself from the situation), but if you were to start doing this regularly, I'd fear for your future employment.