2008 Toyota Sienna I don't believe what I am being told

I drive on a road where I could not possibly have a rock (how big would a rock be) would so disable my AC. It was working fine last Monday as I went to work and back. The next day, I was getting just air. I took it to the dealer because I thought my extended warranty would cover whatever it was. To my surprise, they say a rock hit the AC condenser and it has to be replaced. Total cost $1,200. Not covered by the warranty. One year only? I drove my little Prizm for 11 years, no problems. Took it for service once a year and replace things like tires when they were due.

Just a year old and I am already shelving out 1,200 (I don't have in this economy).

My question is, is this rock thing for real or could it be some defects they don't want to own?

Desperate in Sterling.

Thank you for any tips you may provide.