I can understand how cemeteries can get lost over the course of hundreds or thousands of years in Europe, but it's more amazing to me that cemeteries can get lost in the United States (especially the West or middle regions) during its brief history.  In the story Human remains found at construction site it's reported that in Deadwood, South Dakota, potential "left over" graves from a relocation in 1878 may have been unearthed.  Upon reflection I realize this isn't necessarily a case of a "lost cemetery" but perhaps just an overlooked grave that failed to make it in the move.  I suppose it's not so hard to understand how a tombstone could have been made out of wood which rotted away, or something to that effect.