How was payment made?
If done by check and out of state, that is Interstate Fraud and is actually a Federal Crime. If done In-State, you should contact the local PD or County Sheriff. If you have no documentation (photos before / after, written paperwork ,etc...) it's hard to prove.
If you paid by credit card, dispute the charge w your card provider under product not received, product not as advertised, or Service Dispute. The Fraud department can seize the money from his account and get it back to you
I bought a trailer in Greenup, KY that I began to have questions about prior to pickup. He agreed to hold the trailer for a few weeks before I arrived. Turns out the trailer had been registered w the State as a "homemade" trailer but I knew it was a Haulmark. Contacted the local PD who went on site, inspected the trailer for Man. VINs and found they had been removed. They impounded the trailer and found 2 other vehicles for sale w altered VINs. He refused to give me my money back. Police Chief explained to him the error of his ways, and I had the money returned electronically in 2 hours.