Judging by the trash on his mirror, I would say that he got stuck and then the water came up and silted in the truck...I loaned a 14 foot boat to a guy one time that lost it in the south canadian river..the boat was found a few weeks later about 10 or 12 miles down stream...only about a foot was sticking up above the sand...it had just silted in..we didn't even try to recover it...