My inexperienced opinion is that the aircraft suffered a power loss, although the FC crash is a possibility. Here’s why I think it lost power:
1). Sar104 calculated the trajectory based on it vector when the signal was lost and I found the drone literally in the exact spot indicated by his calcs.
2). If the FC crashed and the drone reset home point and landed, I think I would have seen it hovering. I was flying at night and have found it to be much more visible with the lights than in the daytime, and it was only 300 feet away. It was immediately invisible.
3). Signal loss seems extremely unlikely. In the short time I had it I did some non-scientific range tests. In one instance I was transmitting from between two high tension power transmission lines and the drone was a mile and half away. When I lost sight of it for a a few seconds, the video transmission became choppy. I increased altitude and it returned. You all have flown much longer than me, but signal loss seems to be gradual, not immediate and catastrophic.
I guess the FC crash could be a culprit, and the drone could have attempted to land, crash through some trees and happened to fall on the exact spot it would have if it lost power and fell from the last know height and speed...
FYI. When I recovered it, I replaced the battery which had fallen in the pool. Everything was all broken and banged up, include large parts of propeller missing...and it still flew perfectly (which I did for about 30 seconds in front of me in my living room.)
Just to clarify - if the FC crashes then the aircraft crashes - it doesn't just hover waiting for instructions.