And how did Hackett get Mari's phone number? He told her Shannan gave it to him. Her phone was found out in the brambles with her shoes, purse and clothing, so he didn't have it then. But for him to have it, Shannan was definitely at his house at some point. I wonder if the police ever bothered to ask him how he came in possession of Mari's number to have called her the next day.
FWIW, I do not believe the hypothermia story for a minute. You do not run out of wet, skin tight pants. And she couldn't have ran through there barefoot either, in Thr Killing Season, they both walked through the brambles and were getting torn up by thorns and it was hard going. Rachel even said it would be almost impossible to do it barefoot. And how do you drown out there face up? That's how Shannan was found. IMO