If you are not worried about him retrieving it or training to be a gun dog, have you tried him finding a high value treat? It's a game my boy loves and will keep him busy for a while. Every evening I ask him to sit and stay in the house and I will hide a treat somewhere in the garden, I then come back in and tell him to find it, he is normally pretty quick at this and I have tried hiding it in the herb garden, walking round in different places before I hide it and all sorts! When we are out walking I may throw a treat somewhere as we are walking so he doesn't see me, then again tell him to find it, this can take a while in a large field or open countryside but he loves this game and it does keep him focused on me.