she does not have to be super close to the phone if she lost it- she could have been stumbling around for several days at least if she tried to keep moving, hoping to come to a trail or road. IMO. Wonder if they found anything else on her phone. Another possibility, if she was lying down for the night is that she was startled by something, woke, jumped up, lost the phone, bag, bottle.
I watched the long videos by YTer Rob, linked above. It clarified a few things for me.
He had the data of her phone pings, and her gps points from google maps. Every time she checked for her location on gmaps, that location was recorded in the cloud. It is very accurate, pinpointing exact spots.
It appears she started checking google maps beginning at 3:32 pm, and would check every few minutes. Her last location check was at 4:18 pm. After that, she never checked gmaps again, however her phone did ping with cell towers for a few days, from what was likely a stationery location (so the phone was not dead).
This is why Rob had a strong belief she'd dropped her phone, not too long after 4:18 pm.
It was midwinter in Tasmania, sunset was at 4:50 pm, and it was already quite dark in the forest.
The location where her phone was found, must show the direction she travelled after she had last checked gmaps. They apparently have continued trying to go in whatever this direction is, and by doing that, found what appears to be her bottle/bag..
One can only speculate, but it appears she was trying to get back to Philosopher Falls. Whether deliberately or by acident, she appears to have walked passed the falls and on a stream bed that hugged around a steep hill.
Once she pulled out her gmaps, she headed back towards the falls and, IMO, decided to take a shortcut up and over the hill she had earlier walked around. She got to the top of the hill without it being too bad, but the way down the other side was blocked by crazy thick brush, fallen crisscrossing trees, etc. So she was trying to find her way down when she lost her phone.
JMO