my plane to JFK, which should have left two hours ago, was canceled today, leaving me stuck in goldmining country in California...
I suppose Greyhound, Amtrack and renting a car are out of the question?
He said he's going from California to New York. That would be one long bus ride or one long train ride. I'd rather wait at the airport and let someone do the driving for me.
There are a couple of Amtrak services arriving in NYC at 6:30ish on January 3, but not many tickets remaining. Sou8nds like an adventure to me.
Alternatively, get the train to Denver or another hub and fly from there.