Thinking about their phones: the news media reported that one or both of their phones was used to track their route into the site. But there's no mention of phone data from the campsite itself. For eg, I can imagine a scenario where police could monitor the phone(s) to a certain time when they were either turned off or burned.
This article implies the phones lost cell coverage at the campsite:
Using data from the pair's mobile phones, police have been able to track the route they took to the Wonnangatta Valley, however, once they reached the campsite the phone reception cut out. https://www.theage.com.au/national/...days-before-camping-trip-20200422-p54m7y.html
However, I think the author may have jumped to that conclusion because RH used his radio to contact friends...IMO that was a long tradition carried on in spite of new cellphone technology.
Interesting that RH had a cell phone, but his wife and friend didn't expect him to use it to call them...I wonder how experienced Russell was in using a smartphone, and what kind of plan he/she had.