Given the asset forfeiture laws, he's lucky that they didn't "arrest" the money, and send him on his way without it. In those cases, you have to prove in court, after posting a bond for the money, that the money was not gained in a criminal enterprise. It can be extremely expensive and take months, or even years, to get your money back, if ever.
Mark
You're supposed to legally be able to carry anything up to $10K, but civil forfeiture allows police on any level to seize smaller amounts if they think the source is 'suspicious'. You need to have a plausible story ready when carrying any unusual amount of cash.
“I know you can expect questions with cash amounts over ten thousand, and banks will sometimes hold deposits over 5000 for a while longer, but 4000?”
While you can possibly expect them, you are under no obligation to answer them. TSA’s authority is only to stop dangerous items or people from getting on a plane. They can confiscate weapons or potential weapons and they can stop anyone they think is a threat (drunk or belligerent) from getting on a plane but they have absolutely no right whatsoever to question you about anything you have that is not illegal. It’s what happens when you take numbnuts and give them a badge. Apparently, an FBI agent who happened to be within ear shot finally told the TSA guys they were way out of bounds and they let the guy go. I’d consider a lawsuit.