Unexpected Listener

Driving home from school on Saturday, I was listening to a couple CDs. True to form, I was also singing along (down low, up high, whatever). My cell phone sat innocently (as far as I knew) on the passenger seat.

Upon arriving home...
Dad: Thanks for the serenade.
Me: Serenade? I don't think I was singing much when I came up to the house - I probably did a little bit, but I didn't think it was much to hear.
Dad: Oh, it was about 30 minutes ago.
Me: What? (Confused, but thinking that surely I knew what I was talking about and Dad was mistaken, because I had just arrived home.)
Dad: I was listening to you on the phone for quite a while. I called your name a number of times. You were singing along with some choir.
Me: Oh, my cell phone must have called you.

And I guess that is really what happened. It would have been a prime opportunity for Dad to make up some embarrassing statement that I theoretically made while talking to myself in the car, but he had mercy on me.
It's a good thing my parents' number is the only one programmed to dial after punching a single number on my phone. Perhaps I will leave it that way. Next time I might be saying more than song words - the deep secrets of my life, or who knows what...