We had a Hunter Safety Course yesterday. During the walk through we always have some guy in camo sitting in the background against a tree behind one of the animal 3D targets we have up for the " shoot---don' t shoot" hypotheticals. There were 32 people in the class. Yesterday we had the guy sitting 10 yards behind a wide open deer. He was leaning against a tree dressed in a leafy ASAT suit. We had one small leafy limb in front of him but he was not hidden behind anything. Out of 32 people in the class, NOT ONE... picked the guy up. He was no more than 25 yards from them. I was helping with the range but walked through with the last group. I knew which animal the guy was suppose to be on. I got there and didn' t see him. I thought he had prematurely gotten up and left the spot before the last group came through. I didn' t see him until he waved to everyone.