So, this is an important wording question about RT and the flight - did he say
he cancelled the flight, or that her flight had been cancelled? These sound very similar, and I think most of us would assume that "her flight had been cancelled" would mean that someone called to make the cancellation.
But airlines do cancel tickets if you don't show up:
No-show (airlines) - Wikipedia
I don't remember when BT was supposed to travel, but the airline may have already cancelled the ticket once she didn't show at the airport.
Also, I saw this old post when trying to find her flight date; it looks like the police may have kept RT's cell phone for a while. If that's the case, he might not have any phone numbers to call (Android phones make the contacts available from any computer, but you have to know how to access it):
CA - CA - Barbara Thomas, 69, Bullhead City, hiking wearing bikini in Mojave desert, 12 July 2019
Is keeping the phone for four days normal?