thought that going through assurion was only for lost, water, stolen issues not damage like this, if i was you i would keep asking to escalate the issue further to the next in the chain of command or go to a repair shop and it should be $35 to get it fixed, but paying to get it fixed would be my last option.
***Edit***
do you have TEP? Here is a link to a post that says that if you have TEP that a repair should be free if you pay for TEP, check the post out and even call a repair center and see what they tell you.
http://forum.ppcgeeks.com/htc-evo-4g...ml#post2072618