You will be asked to confirm that it is indeed a no-show, and the order will be removed from the screen.
On the processing orders screen, there is a number that specifies how many orders the customer has successfully processed.
If this number is zero, the customer is new. You can always wait until the customer arrives to start making their first order.
On their next order the number will be one, and you know that the customer is a genuine customer.
365cups keeps a record of all no-show orders in the system. As of April 2012, for every 1000 orders there are on average 6 No-show orders.