Not to come down on you but I think this is a situation that many bowhunters put themselves into. Some spots are hot one year and cold the next. As the others, and yourself, mentioned this could be from a variety of issues. The lack of abundant rainfall, the change in mast production, the redistribution of crops, etc.. all play a part in it.

If you scouted before the season and found very little sign then I would'nt be hunting the area regardless of how fruitful it was for you last season.