Repeat "come" training with brief pauses three or four times daily for perhaps three days. After that, before calling the pup, drag a two- or three-foot trail with the treat. Drop it at the far end. This time, as the pup comes running, meet his nose with the fingers that held the goodie. In a smooth action with the moving pup, bring your fingers down to the trail's near end. The nose will follow. When it reaches the trail, jerk your hand away, leaving the nose smelling scent in the grass. Most pups will follow the trail to the far end where you've left the treat, especially if you've arranged for the pup to be working into the wind. If he does wander off scent, gently guide him back.