They didn't have this gold when CBP shook them down at the border. They came by it somewhere between Georgia and Florida. They were driving back to CA when they got stopped in East Texas. Texas authorities think it was the result of some kind of drug transaction, since a drug dog alerted on the luggage, but no drugs were found. There is more about it from the Van Zant county DA on the internet.
Plus the "dog alert" is a joke: the dogs learn that what excites the handler is alerting to anything they can seize, not just drugs, but money, jewelry or just to please the handler. It's just one set of thieves from the gov seizing valuables from another set of criminals.