it's happened to me a few times and boy does it eat up my battery while it's trying to search for a signal at 37,000ft. I remember one time I'm sitting on the jumpseat and I keep hearing this slight beep. It took me a few moments to realize that it was the audible sound for my phone when it goes in/out of service. I felt like a moron.

Fortunately, after realizing my phone was left on, I'd call the cockpit when it was safe and asked if they saw any changes to the equipment. So far, nothing has happened, but I still don't want to be stupid enough to test the equipment with my phone...