Alright good deal. If he's doing that good you may be able to start some blind reteives. Throw on the other side of your vehicle and walk with him over there to find it. Go back to where you threw it from and call him back. After a short time he will be going over there looking for it on his own. The next day do 4 or 5 in a row the same way then mix in some regular retreives in plain sight. You want to build his thought process up so he can learn to search for it on his own. When he has that down, use a tougher obstacle like a fence he can't see through. Never let him not find it. Always point it out for him and let him get it then walk back to where you threw it from and have him bring it to you.
After he is finding it every time on his own, blind and in the open work on throwing it just barely into thick brush.
Blessings