Also, even if I cancelled the return home, how come that at 51% with the app disconnected the drone didn't go back automatically and start descending when the battery was critical? With 21% I'd have regained the control of the drone and have 30% battery and the camera to see where I landed? Wouldn't you expect something like this is if you buy such a great drone? Would you feel confident that even if I pilot miscalculate something the magic Failsafe RTH kicks in, yes or no?.
The app does not trigger the failsafe RTH. The controller does. Just because the app crashed or disconnected doesn’t mean you lost control. If you had bee in VLOS you could have flown it back.
72m is plenty high to have some sort of wind that you don’t feel on the ground. Any wind would increase battery consumption, it doesn’t require high wind to do so! Hence no warning.
As far as not finding it, who’s to say someone else didn’t find it first?
This is pilot error. You canceled the battery return to home and continued to fly. It sounds like the app crashed and you assumed that it would fly back which is not how that feature works. A little research and reading would have taught you that.