How could a password of a lost ATM card be traced by a culprit?

Tweet

Today I met my friend who has just arrived from New Mexico, USA. She related to me about the experience of her young brother. She's the one supporting her brother for his university education. She sent him his monthly allowance, including his tuition, $ 500. My friend is a teacher in New Mexico, and their parents already passed away after her college graduation. She passed the test for teaching abroad, and she became the breadwinner of her youngest brother. This day, she told me that her brother lost his 2 ATM cards. She learned that her bro put his wallet on the table just shortly, a matter of 7 minutes, while he was searching for his ballpen to list down something. He realized that his ATM had disappeared when he dropped by the ATM beside the food court to withdraw money. He told his sister ( my friend) about it, and my friend went to the BPI bank to report the matter. They learned that the thief was able to withdraw $200. His ATM contained $ 2,000. The password was not printed on his ATM packet. How did the thief know the password? That thief is a tech expert. hoping he will meet his karma.