Thats illegal in the US. They need to have RAS to make a stop. Not just fishing...
He hasn't been pulled over, it's been while he was already stopped that they came looking. And like I said, he finds it slightly funny, "Me? A suspicious character?" He has offered to open the back of the truck a couple of times (he's kinda proud of his "garden shed on wheels"), but I think his casual attitude is more than enough to allay any suspicions.