Bluetick is right, keep on scouting. Bulls will stay in the same area all summer. Find some nice meadow, riparian area, ect and glass early morning and late evening. Spend time looking for tracks in the mud as well. If you have big huge tracks in the riparian areas scout that hard. You'll see the bull eventually.
Bulls do cover alot of ground during the rut. So if you have a rut tag (last week of sept - first week of Oct is normally best) I'd be paying attention to the riparian areas that are holding the cows. The cows don't move much at all and a mature bull will run a route where he checks on the cows to see if they are in heat or not. Normally every couple of days. If you can hunt the rut, call, call, call. That is the key to hammering a big bull in the rut. Cow call is best. A big bull will come into a bull call but smaller bulls figure they are going to get their asses kicked so they won't normally come in.