Is it possible that God really did speak to His prophet, and the prophet spoke what he heard, but it didn't come to pass. Does that make him a false prophet? What if the word from the Lord is a warning? That is what happened in the case of Jonah. God said He was going to destroy Nineveh, and Jonah had to go warn the people. At the end of the day God didn't destroy Nineveh, so does that make Jonah a false prophet?