I don’t think she was alive outside of Utah, the Tetons have really good cell reception. Surely she would have posted something on social media or contacted a family member, just the sheer amazement of your first glimpse of the Teton Mountains is worth a text to someone.Assuming he's smart enough to spoof.
But, in any case, she did have her phone on her at some point, and did talk to her mom. They can ping that phone.