Leaving the phone behind bothers me. It doesn't seem like the actions of someone who is technologically advanced. And, honestly, if I were considering committing a crime and I saw my potential victim holding out a cellphone at ALL, I would give it up and go the other way. I'd just assume they were videotaping me or talking to someone. So, on that note, I agree with you in that it doesn't make sense that someone who catfished them, or otherwise fished them, on the dark web would leave that kind of evidence behind.
On the other hand, I've seen some technologically advanced people do some pretty ignorant things. And I use the term "ignorant" in the most basic definition, not as an insult.
Leaving the phone behind could have been a mistake as well.
I don't think he is reading this board.
At this point, throwing out different theories is kind of all we have. Some make sense more than others.
And I am not over 40.