I have a Lumia 925 and yesterday night this happened to me too!!I left my phone on the desk without looking at it for 2 hours. After this time I wanted to set the alarm but I found my phone off. I tried to turn it on, but I couldn't. Then I tried the soft reset but nothing happened. Then I left my phone all the night (8 hours) on charge, but nothing happened. This morning I tried with the hard reset (using different combination!) but it didn't work.
I've just tried with software recovery tools: but it doesn't recognize the device...I can't believe, this never happened before and I have my lumia 925 since november 2013.
:unhappysweat: