She Was Duped Of N20,000

This morning I went to a POS attendant to make a withdrawal and in the process she narrated to me how she was duped of N20,000.According to her, a young man ( probably early 20s or less) approached her to make a withdrawal of N20,000. After inserting his ATM card into the POS machine, she returned the machine for him to insert his PIN. The transaction was successful with an inscription "withdrawal approved" written on the POS screen. At this point, there was nothing suspicious about the transaction. She counted the money and gave the young man.How did she find out?Well, when the young man left, another customer came to make a withdrawal using First Bank ATM, she discovered that there was no network. If that's the case, according to her, how then did the first person succed (the first person equally came with First bank ATM) when there's no network at all.The above scenario prompted her to check her transaction history. Unfortunately, there was no trace of initial transaction (N20,000). Instead what she saw on the history was a message that the first person has exceeded his limit. Which means the transaction wasn't actually successful but the young man manipulated the machine to look so. At this point, the young man has gone to God knows where. May be to try his luck on another ignorant attendant. According to woman, she has never had this kind of experience. There's no trace of withdrawal but the transaction was successful from the indication on the POS screen.The guy even bought boxers worth N3000 from the attendant using the same money. Here comes my question?How was he able to maneuver or manipulate the POS machine for the " withdrawal approved" message to come up? Mehn, one really need to be careful especially in this difficult moment.