One way of locating a missing phone is to call it. If the phone is nearby, it might be possible to find it by listening for the ringer or vibration. Alternatively, someone might pick up the phone and be able to return it.
Texting a lost phone with the owner's contact information could help anyone who finds the device to return it. Owners can text their lost phones by borrowing a phone from a friend or using an online service to send a text message.
Contacting the service provider is another option. Some carriers provide a GPS location service for locating lost cellphones. Even those who can't help find the phone can often suspend the phone's service to prevent the finder from running up a large phone bill.
Apple provides a feature called Find My iPhone to help iPhone owners find their lost devices. When the phone is powered on, its location is displayed on a map. Owners can view this map by logging onto iCloud and opening the Find My iPhone app.
A similar app, known as Plan B, is available for Android phone users. Remotely install this app on the lost phone using a Gmail account to receive emails revealing the location of the device.