When Hannah is talking to Traci. Lily is holding the phone, then it changes phones. Then it disappears and comes back with the O-phone and disappears and appears many times after.
When Lilly takes the picture of Miley dangling from the air, you can see her Miley necklace on her cheek. When they show the picture Lilly took right after, you don't see the necklace at all. Lilly sees the necklace after zooming in on the picture later. But Miley's necklace was on her cheek, and her cheeks weren't visible, thus making it impossible to see.
Traci's Z-phone is Miley's O-phone. They are the same phone.