What happens if your card is declined at a restaurant and you've already eaten the food?

Your best hope is that the vendor is sympathetic and that your negotiating skills are in order! It’s all about how others perceive you and what their judgement of character is like. It might well be a fault with the bank or the restaurant’s card machine rather than yourself. Once you’ve determined who’s at fault, it’s time to come to some kind of arrangement. Perhaps a friend can help you out by coming to your rescue. Or maybe you can leave an object at the restaurant while you pop home to make alternative arrangements. Don’t forget to tip them for their patience. The manager has every right to call the police though. If this happens, the police usually act as a third party to determine whether a crime is being committed or if it’s just an honest mistake. If it’s the latter, the police may be happy to act as an escrow agent until the matter is resolved. Failing all that, I hope you’re good at washing dishes.