The term "Phantom Vibrations" is nowadays common for a phenomenon usually happened to me as well as a lot of people around the globe too.
Currently no clear explanation has been around which could explain this strange sensation. A survey in U.S. shows that over sixty percent persons have felt this sensation.
Currently it is thought that the nearness of the phone to the body of the person is causing this stimulation. People thought that it was the movement of the fabric of their underclothes or pants. In fact it is not so.
One may have found it as if working throughout the day, sitting in a restaurant or driving. Suddenly you felt the Vibrations and then pick the phone but nothing. No email or message.
Presently not to worry about that those who may have thought this as a mental disorder are going to be relived. Dr Alex Blaszczynski of School of Psychology at the University of Sydney explains that it is related to electronic signalling.
The reason for this above theory was shown as if the sound of the vibration was absent. Presently a term called nomophobia is used to explain this behaviour. But it should not be confused with this phenomanon.
For me it is not more then just our sense of aleart ness to an expexted call or message. Elase it is not to worry about unless you are driving a car in night and took of your sight from the road for one sec to check you cell phone. And next is disaster.