Engine Light

My engine car light came on so I took it back to the dealership today. By the time I got back to work, I got a call stating my car was ready to be picked up. I was really impressed! When I picked up my car I read what the diagnostic test said. "Gas cap was not on tightly. Mechanic tighten cap and test was completed." I felt like a total idiot. I am just glad the car was under warranty because I would have been very mad at myself if I had to have paid to be told this information!