As a licensed surveyor I can tell you that evidence is of the utmost importance in deciding if a corner is obliterated or merely lost. An obliterated monument leaves no trace as to it's original location. If a monument is "lost" there is enough evidence to ascertain it's original location. A drill hole in a rock, or other verifiable evidence of a missing monument should count as a find. Due to the perceived accuracy of our GPS receivers, we tend to give a lot of credence to coordinates. However, coordinates fall far down the list of controlling evidence. "Benchmark" hunting is fun, but to count missing monuments as a find, some hard and fast rules of surveying need to be adhered to. Topo calls to verifiable landmarks outweigh coordinates and measurements. Afterall, anyone reading a chain could mess up, but the "rocky crag" isn't going to move.