Nope, but take the sim tray out and look for the white sticker on the body of the N9 (opposite side of the screen) if its still white you're good no moisture damage(could be liquid) and sometimes in very humid places that happens with out getting the electronics exposed to any sort of liquid. I don't know where you live or how the weather is but its worth checking.
If all that good then take it apart and unplug the battery and plug back in (use good tools, you might strip the screw heads). That don't work then unplug the hardware button ribbon cable its close to the battery, its the left cable on the board if you staring it down. The ribbon cable runs under the board of N9. Good luck. If all fail, Nokia center is the place
ever swap n9 case before? Thats weird, i never face that, and i wont, maybe others can help you