He did not rob you, a robbery is a theft committed with force, he may have committed theft, though in all likely hood, you will be referred to small claims court.
However, you MIGHT have a case for theft by deception. he promised a service for which you paid and he has neither delivered after a reasonable time and he has also apparently deprived you of your property (the chassis).
You would likely need to call the sheriffs office, maybe they will send a deputy. These things are ugly and very hard to file in criminal court as it is usually considered a breach of contract and in some states, a contractor does not have an obligation as a fiduciary.
Good luck!
Please read: [h=2]28-512.[/h] [h=3]Theft by deception.[/h]
A person commits theft if he obtains property of another by deception. A person deceives if he intentionally:
(1) Creates or reinforces a false impression, including false impressions as to law, value, intention, or other state of mind; but deception as to a person's intention to perform a promise shall not be inferred from the fact alone that he did not subsequently perform the promise; or
(2) Prevents another from acquiring information which would affect his judgment of a transaction; or
(3) Fails to correct a false impression which the deceiver previously created or reinforced, or which the deceiver knows to be influencing another to whom he stands in a fiduciary or confidential relationship; or
(4) Uses a credit card, charge plate, or any other instrument which purports to evidence an undertaking to pay for property or services delivered or rendered to or upon the order of a designated person or bearer (a) where such instrument has been stolen, forged, revoked, or canceled, or where for any other reason its use by the actor is unauthorized, or (b) where the actor does not have the intention and ability to meet all obligations to the issuer arising out of his use of the instrument.
The word deceive does not include falsity as to matters having no pecuniary significance, or statements unlikely to deceive ordinary persons in the group addressed.