Almost lost my phone on the mountain last week. Well - I DID lose it, and found it about half an hour later.
Had been hiking laterally above a patch of trees that I suspected deer were bedded in. Sure enough, I spotted a few does about 130 yards out. I dropped to the ground, glassed a bit, and pulled out my phone to mark them on the map. Must have left my phone on my lap while I continued glassing for several more minutes. Eventually, I decided to move on. Made it 30 or 40 yards before realizing my phone wasn’t in my pocket.
As I retraced my steps, panicking, I realized that my Bluetooth headphones were in my backpack and the Bluetooth was turned on on my phone. When I put the headphones on, they say “CONNECTED” when establishing a connection or “PAIRING” if they don’t see a device. All I had to do was turn them on and off while moving. Eventually, it got a connection! Pressed the “play” button and a podcast started playing. Now I was within 20 or 30 feet, and if I moved away from the phone, the connection would get weak. Took another five minutes or so to actually find the phone.
I don’t normally take my Bluetooth headphones on the mountain with me - but I will from now on *just in case* I have to use this technique again.