Well, the mystery is solved. The owner came one afternoon and claimed it. I was already getting offers on it from the neighbors! But the owner told me the story of how it ended up in my yard.

It was late at night and he was driving home in his trailer pulling truck when he noticed flames coming out from under the dash. This was in the boonies, 15 miles from the nearest town of 678 souls, four miles from my farmyard. He stopped in the middle of the road, jumped out and watched it burn. Fortunately for him he remembered to grab his cellphone.

He called the only guy he knew crazy enough to come and rescue him and Wayne (his real name) brought a wrecker and hooked up. Wayne was an old friend of the family and had visited my Dad many times while Dad was alive. So he knew it would be safe in the farmyard until the owner could tow it away. Towing it back to Wayne's yard (almost said Wayne's World)would have taken it miles out of the way.
While it was still on the hook Wayne removed the front wheels thinking they would be a target for theft.

I told the owner there was no hurry getting the truck out of the yard as no one lives there. He was trying to figure out how to hook it to a 3-point hitch on one of his tractors as I drove away.

So no need for CSI or FBI, just an unlucky farmer.

R.