FBI "steals" Civil War gold?

This is just an odd story. My understanding is that Civil War finds are usually considered "owned" by the government? Or is that just on official battlefields?

https://finance.yahoo.com/news/treasure-hunters-challenge-fbi-over-dig-legendary-gold-025045374.html

 

They talk about that in the article. The gold hunters actually just wanted to be a part of the dig and I guess they understood that the government was going to claim the gold anyways, but they also might have gotten a cut. It's just weird, and seemingly unnecessary, how the FBI acted about the whole situation.

 

I think it has something to do with Civil War artifact laws or something? I am pretty sure that if you find artifacts on a battlefield you either have to leave them there or turn them in somewhere. I am not sure if the "gold" was in a recognized Civil War area / park.

From the article:
"The Paradas said they were cheated of a moment they had spent years working for.
"You can only dig the gold up once, and that's a historical moment. And here we were robbed of all that," Dennis Parada said. "I don't understand why they played that game on us.""

"If Union gold was indeed recovered from the woods, the discovery of a historic and extremely valuable trove of federal property on state-owned land would almost certainly touch off a court battle over who owns it, and whether the Paradas are entitled to a cut."

Can you imagine trying to "hide" 10s of millions of dollars in gold bars? Although the vast majority of these "finds" end up being artifacts, not actual gold.

IRS agent: "Mr. Parada, how did you end up with $200 million in your savings account at Bob's Small Town Bank?"
"Well, I did some extra overtime at work...."