Stress can cause a buck to shed early. Perhaps the deer was wounded?? I have seen that before.
Otherwise, I have to imagine that the widespread, persistent drought could be a factor. I think most would agree that antler size did not "jump" this year in many, many cases, indicating that something is holding them back. It also could be that a given buck contracted a non-fatal case of EHD, I would think that would be out there too, with such a widespread EHD outbreak.
Meanwhile, I have found fresh sheds in years gone by while hunting the shotgun season(s), so it happens. Another time I was with a friend when he shot a buck on Christmas morning and when we grabbed his antlers to pull him towards the truck they both came off in our hands, so he had to have been pretty close to shedding naturally.