Thats a tought one. I had the same thing happen this year. Saw tons of deer in september, then about a week into bow season they started mowing and dumping rock in the river to keep it from eroding and i havnt been seeing as much. They seemed to have just moved a lil but it still makes for tough hunting. But another place i hunt is on brick company land so the deer see heavy machinary and deal with noise all the time and dont pay attention to it. Go scout a lil further into the property and find where they went, or get your money back.