The battery on AJ's iPhone switches from fully charged to halfway dead when her mom calls her before she's killed but when the detectives find her phone and gets a text from a friend, the battery is fully charged again.
When Detective Benson finds AJ's iPhone at the hotel clerk's desk. It was ringing meaning someone is calling her but when Benson shows the phone to the clerk, the Lock Screen shows that no one is calling the phone and yet it's still ringing.
AJ's iPhone Lock Screen shows the earth wallpaper when Benson finds it but when AJ's mom calls her and her friend texts her. It shows the flower wallpaper.