Is it the responsibility of the restaurant to ensure that the correct order from a customer is served to him?

To provide more context for this question, here’s the background.

Let’s say you are at a ‘fast-food’ restaurant that has an order counter and a ‘food-collection’ counter. Orders and monetary transactions are made at the order counter and the customer is then directed to the ‘food-collection’ counter to ‘collect’ his food.

As the time taken to prepare the food will take a few minutes, some customers will proceed to look for a seat first, while keeping an eye on the ‘food-collection’ counter. This is where it gets tricky.

If there happens to be a confusion at the collection counter and Customer B mistakenly took Customer A’s order and consumed it somehow, is it the restaurant’s legal responsibility to reproduce Customer A’s order? Or is it Customer A’s responsibility to ensure that he gets his order from the restaurant?