The same thing happens with alot of people I believe. I know it does for me alot of years. Where I live the corn is the biggest factor on the disappearance of good bucks. When the corn height is still small they are all over my cams but as soon as it gets tall enough to conceal their entire body they vanish except for 1 or 2 appearances if I'm lucky. I have found away around this and that was to put my cam in a small island of trees completely surrounded by the corn and realized these bucks hadn't gone far.Not sure if any of my findings or problems may pertain to your situation but I hope it might help you. If you look at my avatar pic you'll see the deer in the bed of my truck and he was one that did a vanishing act as well. Had tons of pics up until the middle to end of July and he disappeared never to have his pic taken again. I actually came home one night at about 2am from a card game and seen him in the headlights along my road in the cut corn that night so I decided to go out and try to catch him slipping back into the woods. At approximately 6:45am here he come right down the trail as if I had scripted it and I killed him on December 9th 2009. Don't mean to babble about my hunt but just wanted to give you some faith and confidence that just because you don't see them or get pics doesn't mean their not there. Good luck to you and I hope you find at least one of them and have a great season.