> Note: A cellphone's effective range for a text message is greater than for voice calls.

Very good point. In this case the cell phone failed at first but worked after about an hour. She may have been wandering in and out of signal. A text message might have worked the first time she wandered back into signal.

I wonder if she tried to use the phone herself? She apparently knew she was lost before the group realised, so if she'd sent a message just to say, "Hey, wait up - I'm not with you" it could have helped. She didn't have to admit she was lost at that point. (I suspect embarassment can contribute to these problems - it is possible to die of embarassment.)

Did she have a whistle? It sounds like she was only a few minutes behind the group at the point she took the wrong turning. That would have been a good moment to sound it.