Photographs, photographs, photographs!
ANY time you get a utility locate, ALWAYS take good pics of the locate marks, being aware of reference points in the background so you can duplicate the situation after the ground is torn up. MANY times we've hit phone cables, called the phone company, and the first thing they do upon arrival is jump out and throw a bunch of paint on the ground. Their new paint often doesn't match the old paint, and how do you prove they're messing with you? With your photographs! It also helps to photograph them throwing paint after the line is cut. I'm not saying that pictures in any way relieve your responsibility to hand dig at their original marks, but if they try to play games with you, those pictures you took will break them of sucking eggs. We're fully responsible for OUR mistakes, but NOT theirs.