Is there something I could legally do with my auto purchase?

We have recently bought a truck from a Guy who works for a leasing company, he bought the truck from his boss ( the company is in cali, i live in vegas) and sold it to us. The title is under the company name. Byrd Leasing LLC.

the truck is an ford f-150 and runs on natural gas. Now we tried to transfer the papers to our names from the dmv and they would not pass the emissions test, they said the gas tank expired last year.
now we tried to go back to the guys house where we traded and picked up the truck and the guy would not give the money back.

is there something i could legally do to get my money back?

No, it is up to the buyer to find that out in advance.