Cars in summer mey get hot - very hot under the Mediterranean sun. Some things you leave in the car on a hot day will look much different after you retrieve them. Exhibit A: This warped Polypropylene CD case is a perfect example of stuff changing shapes when left in the car.
CD cases are usually made of Polypropylene. And this plastic doesn't melt too easy: Polypropylene is heat resistant to temperatures up to 160°C. Yet direct sunlight for hours and the lens effect of the disc's surface cover must have been too much for this CD case. The disc itself was fine by the way.