I've heard of people taking other people's tagged deer while the shooter went to get help to drag out the animal. [:@]

On the other hand, in this case, it's possible somebody drove by the field at 7am and saw the deer laying there.... then drove by 8 hours later, the deer is still laying there and they figure the animal has been lost by the hunter so they took it. Maybe no bad intent, just utilization of the animal. Maybe....