The only people who get to see what treasure is dug up are the people who go out and find it and their buyers.
The government, if they get wind of a treasure being inside a man made vault will claim the treasure and make the area off limits as an archaeological site in a heartbeat.
Now lets look at this from an Informers Perspective :
1: We show a picture of a Gold Bar (which I have done in my avatar) The first question (is it yours?) Hypothetically lets say Yes. Obviously anybody can say it is theirs so no real proof there.
2: In order to prove its yours we need to see a picture of you holding it, and how heavy it is 4lb's and what size 6x2 inches etc.? Ok so you show a picture of you holding the bar, well that's not quite enough for the Feds, even though your holding a Archaeological artifact which is of course illegal.
3: Where did you find it at? so you say it was found in the Caballo Mountains in NM, placing you at the treasure location.
4:What was the vault like, how deep etc, can we see pictures? so you show pictures of the vault, Now the Feds have enough to at least investigate you for disturbing an Archaeological vault which you admitted to having treasure in and removing illegally, this means they are going to be keeping track of your spending which makes it very hard to fly under the radar.
By now I hope I have made my point, no matter how much evidence you show online there will always be skeptics (it was photoshopped, its a fake bar, it was a friends bar not yours etc.) But in the meantime you will be watched very closely by big brother thinking that maybe you really are telling the truth which is not at all good for you as the finder or the seller.