Unfortunately this highlights the reason why extended warranties are a complete waste of money 99% of the time. I made the same mistake myself with my first Mustang. Luckily, when I found out just how useless the warranty is, I was able to cancel it and still recover a portion of my money (at a pro-rated rate). That may be something you can look into, and determine whether you can get a refund for the remaining portion of your ESP. If you still have a loan it will be deposited directly as a principle payment. If your loan is paid off you can use the money to fix the leak yourself.
Frustratingly, the ESP I bought for my 2005 Mustang saved my butt quite a few times. And the ESP on my current 2012 GT also covered a few things already. But this not being covered is really, really bad. I'll keep the ESP, but I'm done with Ford. This is my last Ford product, they just don't stand behind what they sell. And I've never been able to find a Ford dealership that is worth working with. They all attempt to rip people off at every turn.