Considering how much card fraud (and other stuff like money laundering, etc) happens all the time on the Internet and nothing gets done, do you really think someone is going to care?
Amazon uses dummy parcels to catch thieves - https://www.bbc.co.uk/news/technology-46552611
He should buy actual postage and put a credit card inside. All of a sudden, the police should be interested in felony theft / felony mail fraud.