Still in tears & I swore I wouldn't do this because I need time to settle my thoughts, but....
I think she remembered to leave the phones at home, thought the truck (and later the rental) had no GPS/tracking capabilities, but forgot she was wearing that pesky (yet glorious) Apple Watch!!! (Thank you Stave Jobs & @gatorade)
After a BUSY 4 hours she pushed up her sleeve or got an alert and had a huge Oh-$hit moment! I think among other things, this was the reason she got out of that truck in the driveway (solo) and walked in the house looking pi$$ed off!!! Thinking, great now what do I do?!?!? Took care of getting the girls out of the house when they returned from work/school, did a little more clean-up, and set off to think about how she would move Gannon's body from where she'd so stealthily placed it earlier that afternoon!
That evening had to be hard for her to come up with fake concern for "runaway" Gannon, give an initial statement to the cops, and get ready to head out the door early the next morning to get the rental & move Gannon. Meanwhile people are asking her important questions and organizing searches to find sweet Gannon, but who has time for that when you have a body to move?! Hence why she was not involved in ANY searching & seemed "annoyed" during this time period. (There's a special place in he!! for this creature!)
IMHO, MOO, JMO