My brother is a retired surveyor and even he has had problems. He dug out around his pin (don't ask me how, without disturbing it) and poured concrete around it. Then his neighbor came in with an excavator and dug it up. Another good thing to do is to witness the monument to three trees, or drill holes in as many rocks; then take an exact measurement from each. It won't stand up in a court of law unless it was done by your surveyor; yet it will give you something to us if the monument is destroyed. (I believe that there are laws against tampering with survey monuments, but who's going to enforce it?)