Why cant I get the Cops invovled to follow this when it turns out to be a fraud?
Because most likely the person trying to scam you is in Nigeria and the authorities have no jurisdiction in Nigeria. That is why these scams continue to happen. The police/ secret service see so many of these they are buried in them.
And yes, this is a scam, you can tell by the wording and the fact that a "shipper" will come pick it up. The US bank check will be counterfiet and more than the asking price, he will then ask you to wire the remainder of the funds back to him via Western Union. Bottom line, you caught this scam and you did not get burnt. Tell him you sold it locally for cash.