Something I recently learned which is off topic/on topic: "Burners" or prepaid cell phones can be tracked/traced/pinged etc without a warrant by LE. The ruling was, essentially, that someone purchasing a device like this does not have a reasonable expectation of privacy when it comes to the use of the phone and it's location.
LINK HERE Different courts have ruled different things when it comes to the content of the phones such as txt messages etc. I dont believe that warrants covering the information are all that difficult to obtain, especially in a case like this one where the cell phone info of several of the insiders might paint a specific story as to what happened the weekend or in the weeks prior to Cassie's disappearance.
Now in certain states like MA, NJ and MD, warrants have to be obtained first. But I dont think that is the case in AR. In any case, if there was any kind of family or shared plan for the cell phones in the home, I would think that the owner of the plan would have granted access.
I think subsequent phone info on the next set of phones everyone is using, if they changed that is, seems likely to be gathered as well. I wonder if HS needed to turn over his phone to LE?