Reading the report, suggests to me that the lady may have been on a familiar dog walking route and not have been truly lost, It seems possible that she knew her location but could not proceed due to injury received as a result of a fall.

So "lost" in the sense that family and rescuers knew not her location.
But "lost" in the sense that victim did not know where she was, perhaps not.

Telephoning for help would the obvious reaction to such circumstances, but unfortunately her cellphone was lost in the fall.

It seem to me that a couple of red hand flares might have been a relatively cheap precaution. The injured lady was unable to attract the attention of rescuers in a helicopter, a red flare would almost certainly have been seen, as would an orange smoke signal.