I agree with Andy mostly. If I couldn't track the guy down and arrange a trade of all elk meat for the gun I'd either keep the gun or sell it (but I'd keep the money).
What the guy did was a BS move. The fact that he did it to a guy in a wheelchair makes me wonder how he can sleep at night.
The above situation is why I took my big game hunting out of state for the last four years. There are too many people around here and too many people with loose morals in the hills.