The thing is, a well administered operation wouldn't use drones instead of human teams,or dogs, or any other technique. In the best case, all of these modes will coordinate and work together. The drone will see something interesting and a team will follow up, etc.

BTW, I can recall only one instance in which the victim was attempting any kind of signal.



the group was using a signal mirror and it did result in a team responding to their location.These days,most folks are going to use their cell phones, if they can. If a drone UAV is responding to a cell phone call,it might be possible to load it up with supplies.