To anyone who is hesitant about calling the cops about finding a bone, then there must be something else you are worried about. If that was my family members bones, I would want someone to call regardless of how old it is. Any law enforcement or coroner with a lick of intelligence will deduce the proper intel. Hey if they do question you, you might have info, other stuff you found in the area that might lead to an arrest of the suspect, ID of the lost person (someone's son daughter father mother or ancestor). Won't you go to bed and sleep well that night knowing you did the right thing and didn't chicken out? Not an attack on anyone in general, just a call for integrity first, and a positive mote of light on our passions in MD'ing and treasure hunting.
I had a second cousin who was kidnapped and (presumed murdered), the suspect was eventually sent to prison on another charge. While inside he was ratted out by a cell mate for bragging about some murders. This eventually led to his admission of guilt on the murder (he had more than one on his rap), he lead the team out to the site, bones were littered all over in a very disrespectful way. When in doubt ask or speak up.