Replacing Samsung A660, broken LCD screen?

I got this phone about 2-3 months ago, I left it in the rain for a couple minutes once about a month ago, but its worked fine. Last night I recharged it, and today when I open the phone and turn it on the LCD screen appears to stopped working, although the phone still works fine. I can recieve incoming calls, and call other people. I called the Sprint store and asked them if they can replace it, and they told me to bring it in so they can check for water damage. I honestly dont think that water caused my phone to stop working cause its worked fine for a month, but im wondering how will they actually check my phone for water damage. I dont see anything on the outside of the phone that is visible that changes color when it touches water like some people I know do.

Also does anyone happen to know how to reset the phone?

maybe they will open up the phone and see if any of the circuits inside were damaged because of water