BINGO!..
I've researched and the only way for it to suddenly quit pinging is for the phone to have died{battery died or was removed} or the SIM card was removed..
So, at 656 he removed battery or SIM card or coincidentally it "just died" at that moment.. and did not "work" again until 938 pinging in Big Spring at mom's..
I am thinking and this is just me thinking as I'm typing about this new way of looking at things.. That maybe just maybe it was not until SA arrived back home at 1804 Chestnut that he made the determination of what he was going to do to Hailey{possibly in his mind not able to pass up such an unbelievable open opportunity with Billie and David for certain not returning any time in the near future}..cuz think about it this was before 7am..He knew DD had gone to spend nite with friend at 9pm the nite before, he knew the kids were out of school, so most likely he determoined DD would not be getting up for any reason whatsoever at such an early morning hour, after most likely staying up most of the nite with his friend playing video games, etc..So, he knows most likely DD, a 16yr oldboy, enjoying Christmas vacation is gonna be sleeping til noon{SA lived with DD as well so he knew his sleeping/awaking habits, ya know}..That means no worry of DD coming home anytime in the very near future..
Then there's Billie..He knew the car arrangements for Billie to and from work for that day..He had the only working vehicle and would be picking Billie up that nite.so he didn;t have to worry about her possibly coming home unexpectedly either..
So, what if when he arrived there at home he realized it was the perfect opportunity that he could not pass up..
Therefor that is when we see the "break in usage"{IMO battery or SIM out}at 656am and SA puts battery or SIm back in the cell when he is safely at his alibi destination{i.e. moms in Big Spring}at 948am..
Wow, this may be beginning to somewhat fit together..just thinking as I'm typing..I'll have to think on this and see what holes I can poke through it, though before I start thinking anything for certain..