Screen wont turn on

I've been using my N6 unlocked and rooted for 8 months. All was fine until the other day when I got a notification and the led came on but when I tried waking the phone to view it wouldn't turn on. I tried tapping several times, using power button and also volume and power button but no go. At the moment I'm not sure if its in recovery, fastboot etc mode. Can I using adb get the phone back to stock without using the screen. Carphone warehouse won't repair Motorola phones as not authorised and Motorola will say unwarranted if they see its rooted, but that's the whole point in getting a nexus. Anyway lesson learned avoid CPW and Motorola in future.
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