After reading on this site of the big earthquake that may have covered the Lost Dutchman mine, I did a little research to see how bad the event was back in the ‘day’. Here is what I found in part. This very well could have covered the site and or moved any markers.
On May 3, 1887, a major earthquake shook much of the Arizona Territory, southwest United States and Mexico, an area of nearly 775,000 square miles. There are lots of historic accounts of the effects of one the largest historical earthquakes to rock northern Mexico and the southwestern U.S.
Newspapers, oral histories, pioneer journals, military reports, and personal correspondence have been used to reconstruct the impact of the earthquake on communities throughout Sonora, Mexico, Arizona, New Mexico and Texas.
Ground shaking in the Arizona Territory lasted 1- to 3-minutes. Throughout the impacted area, homes were damaged, roads were disrupted, and rock avalanches occurred in nearby mountain ranges.
The epicenter of the estimated 7.4 M event was about 40 miles south of Douglas, Arizona, on the Pitaycachi Fault. The resulting fault scarp broke the Earth’s surface for about 65 miles, with the northern tip exposed just 5 miles south of Douglas. The average vertical offset on the fault was a whopping 9 feet; maximum displacement was between 14 and 17 feet! It is the largest earthquake to have caused historical damage in Arizona – either as a territory or state.
More Info: http://earthquake.usgs.gov/earthquakes/world/events/1887_05_03.php
.