Sorry to say the police won’t really be able to help you. You can give it a shot and call, but as a LEO, if I were sent to that call I’d apologize and tell the complainant that it was a civil matter and he’d need to seek counsel with an attorney. Here’s why, an agreement was made, compensation for a product/service/whatever was delivered, the product/service wasn’t delivered/provided. The details of the transaction are irrelevant because it’s a private matter. Let’s say a LEO does take the case and the matter goes to court. The LEO is going to get subpoenaed to court, and lo and behold most agencies don’t pay their officers for civil court matters. So the LEO knows this and doesn’t want to be sitting in civil court for hours on end with no compensation. I’ve been subpoenaed for civil matters (mostly family dispute) in the past and have asked the attorney that’d subpoenaed me if they were going to compensate me for my representation, some have agreed and paid, others had a GTFOH attitude to which I responded that I couldn’t recall details and ask if they’d actually read my report.
My advice to you is call the local authorities and see if they’ll swing by his place, it’s worth a shot, but be prepared to end up calling counsel. It’s going to be tough (and expensive) if you live in different states.
This is a really crappy situation and I wish there was a way to make it so it doesn’t happen again. Maybe someone at PayPal or whatever can set up a sort of money holding area whereas the payee submits the funds, it’s in a sort of “purgatory” till the payee receives his item and then releases it, or even better corroborate with a delivery service (ups/usps) where the item is scanned as delivered it initiates the release of the funds, kind of like how they send you a “delivered to mailbox” email when your stuff arrives.