Lights have been out in California for decades.
The coins were reportedly stolen from the SF mint in 1905. The perpetrator buried them on the property to avoid being caught with them. He hoped to retrieve the coins at a future date. He never returned, or couldn’t remember the exact spot.
I don’t know what the law specifies regarding the discovery of stolen government property. But if the law states that stolen government property still belongs to the government, the couple is SOL.
They made the fatal mistake of opening their big fat pieholes. It’s a teachable moment: If you find millions in gold coins, keep your mouth shut and sell the coins one at a time to different collectors over a lengthy period of time.