It is weird. I would say since the phone was left behind it should be fair game for analysis. I would assume they’d swab for fingerprints and/or DNA and then access the phone and clone it immediately, so if anything happens to the phone,they’ve got a copy to work from. Obtaining cloud records takes a subpoena, I believe, and they did say in the press release that is something they’re waiting on. For example, he could have deleted data and apps from his phone but they still may be in the cloud somewhere. But I’ve also read Apple won’t easily release phone data so I’m not sure what will happen here if his phone was IOS.
Shoot holes in my logic, but if the cop was able to call Sarah from David’s phone, the phone has to be unlocked/no passcode, or how else could the cop call. Sarah said she saw the name on her phone calling so it wasn’t her calling him it was definitely his phone calling her.