thats helpful to know about your airport! im on the east coast where ppl at airports are often a bit rude, for lack of a better word, or i cant handle the traffic flow.
i actually do agree they knew each other prior (im very much leaning toward in person but could be swayed by some intense texting relationship) but either way, i think they had a very frequent rapport. however, AA still had to come up w a reason to lure/trick/convince her to the park bc even if your best friend asks you to meet at an isolated park at 3am after a flight, most ppl would want a reason as to why that is the meeting place.
so imo, its not so much if/how long they knew each other but why & how she ended up there.
(which my suggestion was if you eliminate any airport discussion, maybe that made planning logistics simpler/faster between them but it sounds like that may not be the case based on the airport pickup description).
Just jumping off from your post.
While this is not my primary theory, if she and he had met before and say went to dinner, maybe even to that park and watched a ball game or had a picnic lunch during the day, maybe to a motel another time, if she had had one, two, maybe three successful meetings/dates with him, she may not have hesitated or lacked trust to meet him at the park even at that hour...
The why still remains of the reason for the park but perhaps he just said my house isn't easy to find, she had never been there and he just says meet me at that park where we had our first "date" and we'll head to my place from there or even I got us a room at a little Air BNB I know of... She does not have fear about it because they had been there before (the park and she had been out/with him previously...)
As for shutting off the phone, like most of us I am undecided there too but I can say when having high stress and being home around family during something like a death/funeral for a few days, all are grieving, others are grieving, I think most of us can relate to how exhausting that is and how ready you are or in need of a break from it... She was used to having her own life and some independence being on year 5 in Utah from what we know. She was probably yearning for a break as anyone would be.
You see a ton of relatives, friends, etc. in the course of a few short days, are on your best behavior and probably helping out as well. I can believe once she let her parents know she was safe, she felt she had done her part and just wanted to shut the world away for whatever was planned, if only through that night, go with him, do whatever was planned or nothing at all and get some sleep... She made her last text to him as or when the Lyft entered the park and my best guess is she then shut it down--as others have said, she had arrived and was with the person she intended to see--that last text/contact is what placed them both there and then they looked further at records, etc. when they had enough cause which showed him/them at his house within 7 or 8 minutes.
The problem I do have here is how fortunate for him--perhaps he talked about shutting out the world to her earlier and taking a "break" from her stressful couple of days... Or it was something she did while with him prior and it was expected or just understood... If I understand it correctly too, in some cases, the one is expected often to give their full attention to the other so no phone upon meeting to show he has your full attention...
I want to stress again this is not my first theory at all but it is perhaps about #3 on my list... My thoughts revolve more around what I think his house really was with its cameras and more.
Just thoughts/speculation and JMO.
Part of the problem is the scale of these objects isn't clear until we find something identifiable.
