CPO Claim Denied

[3Series]

Normally I hate these posts but anyway:

What kind of advice do you have for being repaid a service fee on a CPO claim that was denied as a result of a misdiagnosis where it should have been covered?

1.) Car is under CPO with 45k miles on it.
2.) I developed a small coolant leak that would leave a small puddle on the garage floor
3.) I thought there was a small crack on the expansion tank becuase that's where the fluid was originating.
4.) I brought the car to the dealer since it was under CPO.
5.) Tech ran a pressure test and said it was the lower radiator hose which is not covered.
6.) I paid for 1 hour of labor $150 and took the car to my independent. He said it was the O-ring in the temp sensor which is connected to a hose and the expansion tank. He replaced the temp sensor and all is well. This is also well documented that the O-ring fails.

So, the temp sensor should have been covered under CPO and I shouldn't have paid the $150 labor to the dealer.