This sounds suspiciously like the problem I had recently, although you had run for weeks before the shut down.
Anyway, my problem was caused by the USB charging cord. Of the 6 or seven I have of various lengths, they all had problems consistently running my CHIP (in a Lantern configuration which means I had a backup battery connected to the CHIP). I finally replaced the USB cord with a short Belkins Fast Charge cord. Strange, but true.
And yes after a failure as you had, power up the CHIP from external source then press the power button for several seconds until the CHIP comes to life. Ken