How old was he when you started training him like that? I have a female lab, and typical of Labs, loves to fetch and bring stuff back to you. Like yourself, I started throwing a shed for her (lil over a year old) and she will bring it back all day long. But she won't pick up a shed she finds and I'm thinking it's because she doesn't smell my scent on it, there for didn't throw it so she keeps looking. I haven't been training her like this for very long so maybe she will come out of it. Advice........?