While they are left alone the team is not very far away. I think an hour or so by boat. The contestants are not super far from each other as well but the terrain and walking isolates them. Every mile is a workout. Add to this that the only elctronics anywhere near is on the ship and the camera equipment. I guess what im saying is the drone could easily get caught even if small because if its small it has to be launched closer to the person which means a ship that could get caught. If it has to go a far distance it has to be far larger and it can't blend in to any other electronic/mechanical noise in the area. Lastly they get regular wellness checks which are also inspections so they better damn well hide that shit good.