Bob, in my little understanding of our laws there is no "theft" here. Theft would be a wrongful taking, and he didn't take it, you gave it to him. OTOH there are terms like "bailment" (his custody of it) and "replevin" (wrongful holding of goods) and since you don't mention states, one can only guess your situation is going to depend on the laws of seeral states. Where the boat was picked up, where you reside, where the company is registered, and Texas
to start with.
Then there are DOT regulations
and federal ones as well.
You want your boat? Either pay the man, or find an attorney. While you're looking for the attorney, call the DOT, call your state (and Texas) "Consumer Affairs" departments, and get some idea of what can be done by who.
If the boat is titled property and the title is in your name, you may be able to literally have a Texas
lawman accompany you to the boat and demand the surrender of the titled property. No one is allowed to hold titled property without the title holder's permission, or a court filed lien, or something equally specific. Doing so can lead to an arrest on the spot, which in turn encourages the other guy to play nice much sooner.
And yes, there may be federal recourse if this is seen as "vehicle grand theft" and interstate transport of property over a certain dollar value. The FBI doesn't like to waste their time with anything less than death and explosions, preferably lots of both, but if you can get someone to concede that there has been a federal crime, sometimes you can force them to work on it as well.
Without going into "he says she says" there are obviously some issues of fact, i.e. what does the boat actually weigh? And those can be determined and settled. The fact that the delivery
company has disappeared your boat rather than following normal legal
channels for a claim is going to be held against them. But, you'll need either an attorney to start the ball rolling, or civil authorities (like a local Attorney General to press criminal charges) to get anything going. And the longer you delay, the great the chances that your boat mysteriously gets damaged out in some yard.
Take the bull by the horns, or you'll be trampled by it.
Call those folks up directly, get some answers from them directly. Stop wasting time.