Make a police report.
Ask the DMV if a Release of Liability has been recorded yet by the owner (he's supposed to within 5 days of selling car)
If there is then your name will also be in the data as he would have reported to the DMV who he sold it to and that he's no longer responsible for the car.
Then get a REG 227 form from the DMV - Application for duplicate title.
and a REG 262 transfer and reassignment form acts as Bill of Sale and odometer disclosure.
Mail these to the last know address by certified mail. The DMV will "RDF" for signatures. And they will give you back the forms (with the last know address) so you can mail them off.
If it's returned unopened, don't open it. Take it to the DMV. It shows you did your due diligence of trying to locate the signature.
Depending on the value of the car/truck (is it under $4000?) they will proceed from there in getting you a title.
If there is no Release of Liability and it's been reported stolen, then yes buddy, you've been set up.