Personally, I don’t think it was a Zen master. He or She would more likely have bashed the scorpion with their staff, then whacked the disciple for good measure.
There is, however, a related sufi story about Jesus walking with his disciples when a man cursed him. Jesus responded by repeating a prayer for the man. A disciple asked: “How could you pray for somebody who curses you.” Jesus replied “I could only spend what was in my purse.” So perhaps the Zen master was operating under a similar restriction.