What was Brian doing when the plane flew by and he didn't see it?

Brian is in the process of making a bow when the search plane flies overhead.
Toward the end of chapter 12, Brian takes his spear and hatchet with him to find more firewood and to make a bow. While he is walking in the forest, he almost steps on a ruffed grouse, which suddenly flies into the air and scares him. Brian then thinks about possibly hunting "foolbirds" because they are not very aware of their surroundings. Brian then snaps off a relatively long branch from a tree and attempts to make a bow. As Brian is making a bow, he hears the motor of a plane flying over his head. Brian immediately throws down the limb that he is working on and sprints as fast as he can to his camp. Brian then frantically attempts to create more smoke, but he is unable to get the attention of the pilot flying the search plane.