The affidavit isn't worded conclusively but it does seem that the 6:35 to 6:56 could well be a call (to whom?) and that the break in usage does not mean the phone was switched off. Given that the affidavit states these are phone records, it seems to me on balance they have no more information for the affidavit than you get in your phone bill. The smoking gun in the affidavit is his location at 6:30 in the morning in contrast to his statement he went straight to his mothers.
His phone could have been off, or on and not making calls based on the information in the affidavit. He still had from 7am to 9:30 am to do the estimated 90 minute trip from CC to Lake J.B. Thomas to Big Springs. Sounds about right to me with the added task of getting a body in and out of a car and associated chores.
I'd like to know:
Who did he make the 11 or 12+ calls to? They are in this up to their neck. At one point Billie was interviewed and it was raised that Shawn rang her phone in CC during that period and she expressed (no affect) concern about that if it was true. Ring any bells? I would love to go dig that up, I can't remember if that was Nancy Grace or a BTR show.
I know it is only circumstantial but the phone records before this time would be pretty relevant too, to see where Billie's phone usually was and who was contacted on it, so that one text could be known to be completely aberrant or not. I also hope they paid for their fuel electronically because I think we'd see a major spike in distance covered that week, not only for that potential 66 mile trip but the picking Billie up from work because Shawn had her car is seemingly a very odd "normal" practise - coming home from Snyder to CC to do the round trip again a few hours later? I don't think that happened much before this time period.