3 - 1 in a NBA playoff series is like coming back from being down 13 in the bottom of the 8th in the MLB with the threat of rain out hovering over the ball park. It is a nice win, but short of a injury to Durant or Ibaka, there is no way we win the series.
It has never happened, but if it were to ever happen it would be because of an injury to someone like Westbrook. Granted it would be a lot more likely if it was a one man team and the one man got injured like if Lebron went out after being up 3-0 with the Cavs or something. But you never know.