According to the Urban Dictionnary, a phantom ring is:
Term used to describe when someone thinks they hear their cell-phone ringing or feel it vibrating in their pocket when it's actually not.
"Excuse me a sec... aw sorry, it was a phantom ring." or "Yes! Finally she called me back *reaches in pocket* Dang it.. phantom ring."
Why do I blog this? I like this idea of "phantom" phenomenon, very well connected to perceptual issues in cognitive sciences and the current trend about "magic" in the ubiquitous computing discourse.