Shed hunting the Grasslands

In ND, you can go wherever you want if it is not posted.  Private land intermingled with grasslands is open  unless its properly posted.

It is my limited understanding that you can HUNT on unposted land without permission...doesn't mean you can enter someone's land for other reasons such as removing items from their property (or snowmobiling?...I don't know the rule on that)  I would guess that you could still be cited for trespass, and even theft of property. I know this applies to chokecherries and rocks, which happen to be "wild" but are still the landowner's property. Perhaps a legal beagle can clarify this.... I have also been told by USFS officials that you aren't supposed to pick up sheds, pertrified rock, etc on forest service land.