Michael Hastings Cremated, Family Never Requested; Wife Hires Private Investigator

So, what if I’m a classic car collector and I’m driving up from fla to say Kentucky or Wisconsin with a large (empty truck) to buy several classic cars and just to make the transaction simpler I carry a large amount of cash to buy them with.
If I get stopped by one of these guys are they going to profile me as a drug money mule and take my cash away from me? Do you think that anything I say to them or any amount of paperwork I show them will convince them that I’m anything but a criminal?