Imagine the following scenario:
You are walking along the sidewalk when you pass an unoccupied ATM (otherwise known as a cashpoint machine here in the UK). The light is flashing, and it’s making that beeping noise which brings to your attention that there is a $20 bill in the dispenser waiting to be taken out. There is neither an ATM card nor a receipt to identify who withdrew the funds. You look around, and there is no one coming towards the machine to take the money nor does anyone in the vicinity look stressed from losing something. You are the only one who has noticed that something amiss.