The taking of her cell phone does indicate it probably was someone Allison knew and had incriminating evidence on her phone that could tie the murderer to the crime. Why else take it? Any half witted burglar, random perp, serial killer, neighbor, ex, etc., would know that they couldn't use it, sell it, recycle it. To try to do anything with that phone after the fact would be like carrying around a red flag saying "I did it!" "I did it!"
No, he didn't 'steal' the phone. He took it so that no one would be able to see things on her phone that could identify him as the killer.
Or possibly he had taken the phone away from Allison and disabled it by breaking it or even removing the SIM card or damaging the battery by soaking it in water. Any of these things would have rendered it unusable and undetectable by GPS location services or Find My Phone apps, etc.
Anything that had been backed up the the Cloud which is what happens when your phone is plugged into the charger and connected to WIFI would still be there. There is nothing the killer could have done about that. Even if he did a reset. Also, her carrier would still have all of her calls out and calls received information as well as texts sent and received.
It would not have brower information however. So if the killer was browsing the internet for ways to destroy DNA it would not have that. But then again, the phone was probably disabled before he killed her so that's probably not the case here.
If she kept information on Notes that information may or not be stored on the cloud. I'm not sure.
But for sure, whatever the reason, the killer took the phone and has probably destroyed it and disposed of it in a manner in which it will never be recovered. (the phone, not information that the carrier, cloud, etc. has).
It's really too bad we don't know if the mother spoke with Allison at 8:00 p.m. MN time or if there was a text exchange at that time. That would give us some time frame in which we could sleuth better. The reason I say this is because it would tell us if the killer might have actually been there BEFORE that call or text, providing her mother didn't actually speak to Allison or maybe her text didn't go through but that was never mentioned.
For those of you who wonder what the 'not delivered message' on the dad's iPhone looked like, here is a pic:
FWIW: I sometimes get that message when I don't have a strong enough signal wherever I am to deliver my text. So, if the mother was flying and tried to text Allison she might not have thought too much about getting that 'not delivered' message, if she did get it. imo
