If there was gold, the FBI would have confiscated it had the men actually found it, anyways. The gold would have been covered by the FDR era gold confiscation law.
The FBI just saved them a ton of work and expense for nothing.
Whether or not the law was Constitutional is another matter................
One article said "the finder said he was there during the dig."
No, the treasure hunters know that. They’re just trying to get the finder’s fee for helping with the recovery of gov. property (some percentage).