Long-time lurker, first time poster. I've read every post on all 4 threads.
Here is a thought.
When KR texted her mom and realized that her mom was essentially going to sleep ("wake me when you get home"), it gave KR a little extra boldness to push the curfew. Therefore, as the party was breaking up/splitting off, she calls SS to be sure she did indeed get out (as she is a conscientious friend), then proceeded to turn off her phone preventing her mom from looking back at her locations the next day. I do this with my kids- I frequently look back the next morning on their routes/locations/times for the night before to make sure they did what they told me they did when they told me they did it. How clever would it be to just turn one's phone off, go to an after-party, then sneak in MUCH later than curfew while mom was asleep. The next day you could claim the locator app glitched, you don't know why it still shows you at the campground, you don't know why it didn't show you driving straight home at 12:30. Just a theory as a mom of teens.