While London and Maddie are locked in London's closet, London gets on Maddie's shoulders to get a signal on her phone. When the phone dies, she shows it to Maddie, but you can still see that the screen on the phone is on.
When London and Maddie are locked in the closet, London makes a call on her cellphone. Then the phone dies, and as she tells Maddie that, you can see on a picture on the back of the phone. So actually the phone is still on.
After Zach and Cody get back, they supposedly run upstairs. But when Arwin is trying to get the machine to work, Cody and some camera equipment is reflected in the glass.