dont know why you are worried personally, but first of all does it vibrate after soft reset liek it is booting up cause if so your screen went which is common with them damn ribbon cables.... but anyways nothing to worry about, if you come in there and the phone isnt working at all they will just give you a different one without questions..... basically what they will do is go back there and try a different battery and see that it still doesnt respond at all and not want to waste the time trying to figure out what went wrong on it.... to be safe you can place the phone in the mocrowave for about 2-4 seconds until you see some blue smoke and than the internals will be gone and there will be no sign of you messing with it :) but i wouldnt even do that since i know that you will get a new one.... and also you can make the claim for free and have it overnighted to you by going to this links and following the steps for the claim center form.
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http://www.nextel.com/en/services/service_repair/self_service_solutions.shtml