It was a common practice for the family to visit the graves of friends and relative, and have a picnic around the grave(s). It was also common for a surviving loved one to return to the grave, and bury something that they thought belonged to them, like a piece of jewelry. With many (if not most) of the older sites, the graves you can actually see are just the tip off the iceburg, with a large number being in unmarked graves. I have located many unmarked graves in these areas over the years for local churches or relatives, but never had to do any digging. Nope, wouldn't go there. And, on many occasions, these unmarked graves were outside the walls surrounding the marked graves.
It was mentioned about an old tin-type photo was found, well, this is possible maybe in some places. The tin was usually painted black, and as long as the tim didn't rust, they might survive. I have a couple of deguerreotype (1840's - 1860's) that came out of a trash pit that had been buried for about 130 years, and you could still see the images.
Have I ever searched a cemetery? Nope. I have hunted the dirt roads and the surrounding areas, but if I ever saw anything that might be a grave, I would leave. Keep in mind this though, with the exception of family cemeteries, most cemeteries had a church in close proximity. This is what I look for, NOT the graves.
