@Joe Dohn I'm having exactly this issue right now, except my ipad has not miraculously awakened as yours finally did. Am curious -- did you ever figure out what was wrong? Does it still work? I'm still hoping that mine is revived but the Genius Bar thinks its a dead mainboard. Sucks, I did not get AC+ b/c I am super gentle with devices. Can't see why I'd risk an iPad purchase again, but I very much want to revive this guy!
I couldn't figure out what EXACTLY happened, but apparently, when you connect an iPad to Apple's diagnosis software, it sends a code to check for corrupt files and restore them. If the iPad is bricked due to corrupt files, doing so will attempt to reboot and restore it -- which could have been my case. Maybe if you bring your device to a dealership and ask them to check your device, your device too could also be revived if it's not turning on due to corrupt files.
Also, try leaving your iPad charging for 24+ hours and then try to reboot it to see if it responds.
And yes, my device still works as if nothing happened.