I'm still trying to figure out what could have happened.. Was the A T and T network overloaded? or maybe hacked? Bad phone firmware? Were other networks good at the same time?
Lost backhaul. The cell site is still powered up, but nothing to connect to. I experienced that with a NexTel site many years ago. Phone could see the control channel, but no way for the traffic to get anywhere.
Garmin in-reach as the best option, if affordable.
I'm happy with mine, but a new one is around $300 (unless you find a sale) and you still pay around $7.50 a month for basic service.
The chances of all cell carriers going down at once really depends on a lot of things. Easy for one carrier to go down due to simple failures or backhaul issues. Carriers might be sharing towers locally, but that's not always the case. Backhaul can use a lot of mediums, fiber, RF links, microwave, etc.
Last I looked, FCC had some requirements that cell sites have 8 hours of battery backup minimum. In California, the PUC has mandated that most have back up generators with onsite fuel storage to extend run time in emergencies.
Still, a lot of things that can go wrong, but cell systems are not as fragile as all want you to believe. But having your own redundancy is a good plan if you can't survive with a connection. In Kevin's case, and his wife's medical needs, having some alternatives is a good plan. Since budgets are real, not everyone wants to go with expensive solutions for the rare cases that a system might be down -and- an emergency is needed.
An unactivated cell phone on a second carrier is a good option.
Going next door and asking the neighbor to call, either on their own cell phone with a different carrier, POTS, different internet/phone carrier, or whatever is another 'free' solution.
Eventually we can dig down far enough that we can imagine every single service failing, but the reality is that is unlikely.
At least this hasn't deteriorated into someone telling you to just buy a Baofeng or hacking a ham radio and programming it up with the local public safety agencies frequencies….