If nothing was found , there should be no criminal investigation . If something was found at the site, then there is a investigation.
That is not how a criminal investigation works on both points. I can directly speak to this as a LE Officer of 11 years. We do not need to find anything in order to open a criminal investigation. Nor do we necessarily close it if we find nothing. This is how a typical investigation goes:
1. LE receives a complaint or a tip that a crime may have been committed. In this case, when you told the FBI you possibly found stolen civil war gold and possible human remains at Dent's run, you were the one making a complaint.
2. After LE receives the complaint, and we have reasonable suspicion a crime may have been committed, we begin our investigation. We do not need to have found anything yet to open our investigation.
3. LE then begins interviewing witnesses, doing research, running background checks, visiting potential crimes scenes, gathering evidence, documenting the scene, processing the scene, report writing etc etc.
4. If the evidence points to a particular suspect, an arrest may be forthcoming. If the investigation is for a potential crime committed a 150 years ago, our focus will be more on evidence gathering, historical research and piecing together what may have occured and who may have been involved.
5. In cases where no or insufficient evidence is found to conclude the investigation or make an arrest, we do not necessarily close it. It then may become an ongoing investigation.
LE doesn't just take the word of a Treasure Hunter, dig at one site and then say whelp, that's it, case closed. Their investigation is ongoing. That's how you solve a crime, you don't just close up the investigation at the first dead end you find.
In the case of Dent's run, since you have no access to the FBI case files, the ongoing investigation may be because they did find fragments of evidence that they are processing and researching or they may be following other leads the evidence pointed them to. There are many, many reasons their investigation is still ongoing. And here's the kicker, at this point, their investigation may have taken a turn towards something that has nothing to do with the original complaint you made.
What i sincerely don't get FindersKeepers, and i'm not trying to insult you in anyway, i'm trying to help, is why the basics of how investigations work and how court cases work evidently haven't been clearly explained to you by your counsel? Your counsel should be explaining these processes to you, and if not, don't be afraid to ask your counsel the tough questions, that is what you pay them for! Remember, they work for you.