The only possible use for her phone on the ride that she was going to take would be to catch Spotify or some other channel on her direct satellite internet connection (if they had it at their house) and receive it via her own wi-fi unit. If she had an extremely good unit, she might get good reception for a thousand foot radius of her house, and spotty coverage as long as she was in "line-of-sight" of her house.
However, she would be a fool to do it, because the phone would quickly wear down it's battery trying to find a cell tower to "ping". If she ascended clear to the top, she might find pockets of good cellular connection with the A,T&T tower along the Monarch Crest Trail; but we know that she wasn't planning on getting to the top, as it was deep in snow on May 10th.........ideal for fat-tire bikers but not passable for her on a conventional mountain bike.
I'm going to stick with my assumption that she most likely did not have her phone with her. As I stated before, if her phone is missing with her, that alone might be a telltale clue. IMO
No, once again, you are wrong about what the phone can do. I have YouTube Premium, I download all kinds of things to the phone. Therefore, when I am hiking, I can listen to Tricia on Websleuths or my favorite TV critic. Mostly I listen to audiobooks (I have 10-11 of them just on my phone). I do not need any sort of connection to do this. Just bluetooth for the headphones.
Why wouldn't I do this? It's an important thing to me. While I no longer bike much, I have plenty of friends (and students) who do. Who are women. I do not know where your data on women and phones are coming from, but I'm telling you I know lots of women and many are in Suzanne's age group. Some are in Colorado. We all take our phones on hikes and bikes - for the reasons I just mentioned.
Our batteries do NOT go dead
ALL of these use their phones to broadcast to their airpods (I use Beats).
They don't do it every single time, but on any given day, I see dozens of people on the track doing laps with their airpods and their phones. We constantly discuss which shorts are best for women (men's usually have a pocket - women's don't, so we figure out which brands do have pockets suitable for phones and gift each other with them).
It's a huge use of the phone. PLUS many people are also FB/Instagram uploaders who constantly take pictures on their bike rides and runs
My phone can go 12 hours in the Sierra with no cell service and still be working at the end of the day. Mine is not the latest model. My daughters both have phone cases that provide additional battery at very little weight (and no one I know cares about the added few ounces of the phone or its supplement battery). I know men who do this too.
You do not need wifi to play podcasts or audible or youtube on your phone. It does not wear down the battery or my phone would be dead frequently. I even checked yesterday - after several hours of streaming, it went on its charger last night with 60% still available.
You do not need cellular to listen either.
There's absolutely no reason to believe Suzanne intended to go "to the top" of anything. Unless you want to claim that a seasoned Instagrammer/Pinterest/FB user doesn't know how their phone works, Suzanne would also have known to turn cellular off (mine is off most of the time - I don't need it). My watch reminds me to turn it back on when I get in the car. Otherwise, it knows what to do (connect to wifi) when I get home
It's easy peasy. Now, if Suzanne is the type who prefers absolute silence while biking, that's another matter. But the presence of airpods and Apple watch in her life tell me that she very likely listened to *something.* I have downloaded music, too - and sometimes I do that, it's just as easy as listening to Websleuths Radio.