This happened to me around the same time you posted this! My phone has yet to turn back on will not charge or reset.
Holding the power button and home key until the apple symbol appears on the screen seems to reactivate the phone.
This has happened to me twice now within about a month or so. I'm a "hit any key" type of person, so I stumbled across the fix. However, my question is will this likely continue and is it time for a new phone? I'm eligible for an upgrade but, other than this issue, have no reason to upgrade. I like what I have. If I do upgrade, will likely go with the 5/5S. I guess, in short, the question is does this mean the 4 is dying?