Would you claim a prize you actually did not win?

For example, you walk into a new store that opened a short time ago in your area. Right before you entered another person enters but heads to the restrooms near the entrance instead of the interior of the store. As you head for the heart of the store to do some shopping, you are stopped by clerks and the manager to the sound of music and falling confetti, are told that you are the 500th customer (they missed the person heading for the restroom) They tell you that you won a $500 gift card to the store, and a $200 visa gift card you can use in any store that accepts visa. Do you keep the prize or tell them the actual 500th person to enter the store is in the restroom and describe what they are wearing so when they come out, they can be properly rewarded?