Oof, that sucks.
A few general observations for travel in the backcountry, in no way meant to comment on this particular incident -
Having a cell phone on hand *might* be useful, because you never know where you might get a small patch of connectivity. If you go into nature to get away from all that, that's fine - just leave the phone off unless you need it.
In the backcountry, changing a plan by splitting off solo increases risk.
Devices such as the Spot or InReach are too expensive - until you need one.
Anyone can be in an accident, no matter how experienced or fit you might be. (Yes, YOU! And me. Anyone and everyone.)
I consider it mandatory to tell someone back home that I expect to be back by X day/time, and that they should be concerned / get help if I'm not back by Y day/time.