Since there's no CMONEX or anything.. you should be ok just bringing it back to Sprint store.. just act stupid. Be like, "I plugged the phone in, and it wasn't doing anything, so I unplugged it, and started trying to get it to work, just taking the battery out and pressing random buttons all the time, and this showed up, and I can't get it to go away! What the heck? Can you guys fix it?"
Lol.. it'll work. I promise