Connecting training in customer ervice to the bottom line

Three people were standing in a line at a discount store, and the store was about to close. The clerk suddenly announced that she had to take a "lunch break", and would only help the first two customers. The third customer announced firmly, "But I have been standing in line waiting for several minutes!" The second customer, not wanting to deal with the conflict and also furious with the store clerk, replied to the third customer, "I will go into another lane, and then you will get waited on." A few minutes later, the third customer had been waited on and saw the second customer still waiting at the end of another line. She mouthed the words, "Thank you!" and left the store. The second customer commented to someone nearby that she would not shop at the store again, and would tell others about the poor customer service.

Apparently the clerk had not had her break that shift, and, instead of notifying her supervisor, decided to close her check-out herself. If you were the manager, clerk or one of the customers, how would you have handled this situation?