Legal analysis: it is found that someone else's bank card is not returned and used to withdraw money, which constitutes fraudulent use of someone else's credit card. This behavior of taking other people's money has been suspected of breaking the law. If the amount of fraudulent use by a party reaches more than 5,000 yuan, it constitutes the crime of fraudulent use of another person's credit card as stipulated in China's criminal law and should be sanctioned and punished by the criminal law. Therefore, when the parties find the bank card, they should actively look for the owner or hand it over to the local public security organ for handling.

Legal basis: Article 5 of the Interpretation of the Supreme People's Court on the Applicable Law for Handling Criminal Cases of Impairment of Credit Card Management uses forged credit cards, credit cards fraudulently obtained with false identification, invalid credit cards or fraudulent use of other people's credit cards for credit card fraud. If the amount is more than 5,000 yuan but less than 50,000 yuan, it shall be deemed as "a large amount" as stipulated in Article 196 of the Criminal Law; If the amount is more than 50,000 yuan but less than 500,000 yuan, it shall be deemed as "a huge amount" as stipulated in Article 196 of the Criminal Law; If the amount is more than 500,000 yuan, it shall be deemed as "extremely huge amount" as stipulated in Article 196 of the Criminal Law.