I'm not entirely sure of the legalities here: would he have been allowed to dig up that gold? Would he be entitled to a finder's fee from the FBI? Reporting it instead of digging it up may well have been the right thing in this situation.

And if the government had excavators, an army of trucks and possible other machinery, as the article suggests, then I don't see why they wouldn't have been able to extract 7 tons of gold in one night. And a lone treasure hunter may not have access to such resources.