Thanks for posting Superfly.
All's I can say about this is that people are know to go onto private land, or Native American Lands and pick things up or dig in the soil to find artifacts.
These include arrowheads, pieces of pottery, beads or any other thing of what someone might construe as having a monetary value or collection value.
Usually, picking things off of these lands is an illegal practice. People found having done things like I mentioned are normally taken to task at the fullest extent of law, that is, serving time and paying restitution and damages.
Just disturbing artifacts found can get a person into deep sheet. How do I know this? I turn your attention to the scout master who disturbed a rock in Utah. Although the charge against him was dropped, what he did, unknowingly was a felony.
Ex-Scout leaders charged for toppling ancient Utah rock
Here's a story related directly to the thread subject;
Arrests Made In Sale Of American Indian Artifacts : NPR