In Colma, "City of the Dead," home of 16 cemeteries, only one special grave marker has been dubbed the "Mystery Tombstone." It's the headstone of H. J. Hartnagle, dead since 1875, and buried somewhere...else. The Mystery Tombstone stands outside the Colma Historical Museum with an explanatory plaque.
In the 1930s, courts decreed that there was no room in San Francisco for buried dead people (cremated remains were a different matter), and ordered all bodies and their grave markers moved to Colma, southwest of the city. Hartnagle's remains were exhumed from S.F.'s Odd Fellows Cemetery, but somewhere in transit to Colma he was separated from his headstone. Whoah ho! Wacky sitcom concept?
No -- just the kind of loose end you'd expect in the mass migration of dead people. It's amazing they didn't get everyone all mixed up (but then again, how would we ever know?). The Hartnagle headstone turned up in 2001 during tunnel excavations "near Holy Cross Cemetery along the old Southern Pacific right-of-way," according to the plaque.
"It may have accidentally fallen from a railroad car or may have been discarded as many tombstones were when San Francisco cemeteries were evicted." You can sometimes see old tombstones used as fill down in the Pacific Ocean surf, or as part of odd art projects.
So where's Hartnagle himself? They say he's in a mass grave at Odd Fellows (Greenlawn) Cemetery. Sure.