I had the same thing happen a few weeks ago. I heard a bang on the freeway at 75MPH and looked in the rear view mirror just in time to see the little Porsche crest flying away. Luckily, I have a spare set of center caps because I bought a second set of rims. The center caps are easy to get off with a wire hanger, there is no need for a special tool.
Just bend the wire so it has two 1/2" feet pointing in the same direction, insert them into the holes, and pull, the cap will pop off. Good luck getting it fixed, and if you find someone that sells just the crest let me know.
