This is an excerpt from The Complete Whitetal Addict's Manual, it is copyrighted and cannot be copied or printed wihout written permission of the author, I give permission to use it here.

The Dispersal Phase
I often hear hunters say that (during the hunting season) they can’t find the big bucks they saw while they were scouting from late August to mid-September. That’s because the bucks probably weren’t in the same area. Once the bucks (that you may have seen in bachelor groups in late summer/early fall) shed their velvet, they start to become more aggressive, and eventually they won’t put up with each other. While some of the bucks may stay in the same area, many of them move to new core areas, where they don’t come in contact with other bucks.
Some of the bucks may move out of their summer home range to go to their fall home range, which may be as little as a half mile to as far as several miles away. This breakup (dispersal), and fall home range shift, usually occurs within two to three weeks of when the older bucks begin to shed velvet. In the upper Midwest it generally occurs sometime between the first and last week of September. By mid-October the bucks have usually moved to their fall home ranges. If you plan on hunting after October 15 you may have to start scouting all over again, because the bucks you saw and hunted from late August to mid-October may have moved to their fall home ranges.

Since bucks usually start making new rubs and scrapes in the areas they use in the fall, the best way to locate them is to look for fresh rubs and scrapes. When you find fresh rubs and scrapes, in areas where they may not have previously occurred that year, you can setup where you can watch that area, to see which bucks are there. Once you find the buck you want you can backtrack its rub route to locate its core area, where you can setup to take the buck.

This is EXACTLY the situation that is happening at my place... get some GREAT bucks on camera in June/July/Aug and Sept they disappear never to be seen again

well over at my place im worried about my bucks. Basically Im just not seeing any. I have hunted this place for 12 years and my family before me for 45 years. Never have we ever gone a hunting trip without seeing bucks, so i know they are usually there. well about 4 years ago we invested in some trail cams and they proved to be a great scouting tool. This year was the 1st year they went up before bow season, oct 15th. And Im just not seeing any bucks on them. Im hoping that they are just not moving yet or they are still migrating in. I think that im just nervous because this is the 1st year the cams have been up all summer but i really wish a few bucks would pose for the camera to settle me down.

I think this is a correct understanding and explanation of what has happened to the bucks I was seeing for months but now am not. I know they are in the area because I have walked the area and have seen good scrapes spread out over about a mile wide area and new rubs. But they do seem to be looking for their main core areas all around me,so I will learn from this artical and see what happens.

This is exactly why I hunt so hard the first two weeks of the season. Here, once October hits, it's doe killin' time for a couple weeks...

Also take into account in the upper midwest the bodies are changing, they change from browse to other food sources that put on fat. They will also start energy conservation facing the impending winter. A lot goes on this time of year.

I find getting bucks on trail cameras sometime is as hard as hunting them I have had strange luck as well with cameras. In the spring, if I put out salt for the cameras and if it is near where bucks travel I'll either get nothing or an entire bachelor group. I also found bucks are always moving differently then I expect. For example I had 95 pictures on a camera that was on a trail to a seep and in just a week with only spiker bucks and does. I bought a better camera and noticed there were a lot of pictures with no deer in them then I realized there was something deeper in the woods paralleling the trail. So I moved the camera for a closer look (so it was facing away from the trail) and voila there were the big boys walking parallel to the main trail (but on the upwind side....I think they were going to a different place because if you ask TR they are usually on downwind side to smell the trail). Then in another instance I put a camera in a wide-open place where a ATV trail met a field and 5 bucks were crossing over the ATV trail like clockwork because it was some kind of funnel for them to go from slough to woods. That was total luck on my part. When I put cameras on rub route they are usually vacant until certain times of the year.

I think once I nail down how to get bucks on camera consistantly I will be able to arrow them consistantly lol.