The truck driver said he was traveling alone, he had correct papers, etc, the FBI checked the truck/van and found the two ME guys.
My take on this is the FBI was involved early on and this was an ongoing investigation. Hey look here everybody we caught some terrorist, showboating IMHO. The FBI just doesn't give out info like this unless they want publicity. Like the ATF at Waco, inviting the media to record the raid when it went all wrong.
maybe they were the cargo, and technically he was the only occupant of the "truck bench seat"