Not sure if it was mentioned or asked. From my experience on updates of dji go app or firmware, many settings changed without warning. One being my 120 meter max changed to 250 after an update. Along with other settings, also settings displayed in app when drone not connected are different that what is actually programmed on drone.
So when the OP says RTH was the setting on signal loss, is that what you remember setting it to? Is that what you seen when you turned on the controller when you were searching and seen that while the drone was not connected? Or is that the setting you seen after you found the drone and connected the controller.
After reading the majority of the posts here, I would surmise that the drone simply landed. Landed due to low battery because the setting at some point for RC signal loss was reverted back to "hover" this is backed up by two very important facts. 1. All debris was located in same spot and it was not in an elliptical pattern over 20-30 feet. 2. Witness seen it fall from sky. I challenge the word fall from sky, if it actually just fell, the likely hood of someone hearing It, turn to see it, and figure out what it is is very slim. However, if it started to land and slowly as they do, there would be sufficient time to hear, see and figure out what it is.
Think about how many times you have seen some flash across the carpet, and thought.... was that a mouse? Naaa can't be...
3. Data retrieved from controller has battery level of 40%? Or what ever it was. This is due to the RC signal loss.
4. Telemetry data was probably looked at by the OP when he recovered the drone, and seen this very entry, RC Signal Lost then....Low battery LAND. ?
5. Is the telemetry data kept on the SD card or internal memory on the drone? if so, OP probably kept the SD card before sending it in for repair.
Regardless, glad you found it, I always worry when i'm out on a hike, and the thing is so far away, and even farther up the mountain, I think, if it were to fall, would I want to go climb up there...