Picking Up An Order Out Of Order

(I am assisting with a couple and a lady walks in, takes a menu, and steps to the side to read it. She is roughly four feet away from the counter and not in the center of the room, but to the side. After I finish with the couple, I look toward her and note that she is still looking down at the menu. One new customer walks in, and she looks ready. I wait a few seconds for the lady to finish, but she is still looking at the menu, so I decide not to interrupt her and smile and nod toward the new customer.) Me: “Hi, how can I help you today?” New Customer: “I’m here to pick up an order.” (It takes me around one minute to assist her with that, and right before she is about to leave, the first customer has finally finished reading the menu, and looks up, shocked. She storms up to the counter, right next to the new customer.) First Customer: “Hey, I have an order to pick up!” Me: “Oh, yes. What is your order?” First Customer: “I came in here first, but you let her in front of me, so I want to cancel it!” New Customer: “I am so sorry; I thought you were still looking at the menu.” Me: “I’m sorry. I thought you—” *she storms out* “—weren’t ready.” (The new customer continued to apologize to me, but it really wasn’t her fault. I have no idea which order the lady wanted canceled.)