If you have access to trail cams they could take some of the guess work out of it. I'd be guessing but I would say a mojority of your big buck activity is happening at night. Here in Mo the rut is on, bucks are stupid and are being see all day long. During our pre-rut I only got big buck pics at night on my camera. I would say they are there they just hide too well. Try to find a bedding area or a scrape line, or make a mock scrape and put a camera up. This will let you know what is using the scrapes.