Loss of T-Mobile service?

As I drove to work in Menlo Park this morning, I was unable to operate my cell phone. I tried several numbers from my phone list and typed others. I turned the phone on and off and even tried to call T-Mobile. Each attempt was met with a message about the number being unregistered. It was a very strange feeling to be unable to talk on my drive and my car seemed particularly quiet. I have not been able to find information about the disruption on the T-Mobile website. Does anyone know anything about it?