Joke

My girlfriend called me as she was driving to an appointment. She arrived, and I could tell from her voice that she was getting frustrated. Finally she said, "I know I had my cell phone with me. And now I can't find it!"
I replied, "Aren't you talking on it!?"
There was a solid period of stunned silence as the reality of the situation sank in - followed by, "You are NOT going to tell anybody about this!"
A true story if you can believe it. Want to guess her hair color?