Current does not add up to zero when 3 phase is shorted.
What you will get is a BANG ! That will have ringing in ur ears and if you lucky enough not to close ur eyes, you will be blinded for a minute or too. And if you are alive, the following night, be prepaid for some serious eye irritations that can barely make you open your eyes.
Before you ask why, I would say, Been there Done that.