Elisha told the messenger to tell the king not to worry because by tomorrow food would be cheap and plentiful in Samaria. The messenger scoffed, so Elisha was all, Fine. You will see this miracle, but not eat of it.
Next morning, four lepers, who by law had to be homeless at the city wall, decided that they would go throw themselves on the mercy of the Syrians, since all they could do but die, and a quick death was better than starvation. But when they got to the camp, they found it deserted–as if all the humans had simply vanished. So the lepers ate and drank their fill and then started carting off and burying all the silver and gold they could find…but after a hour or so they started feeling a bit guilty…and when the disappearance of the Syrians was discovered, they would probably be punished for not telling anybody. They decided that they should better go spread they word. So they went and told the gatekeepers, who told somebody else, etc. until word made it to the king. The king was all, this is probably a trap, but he sent out some men on a couple of the remaining horses to scout for the Syrians. The scouts followed the Syrians trail of discarded items all the way to the Jordan, then rode back with the wonderful news that they were really and truly gone!
At this, people mobbed the camp like it was a mall on the day after Thanksgiving. In the stampede, the scoffing messenger was trampled to death.
As for the Syrians, God or Elisha or some bad rye made them hallucinate that they were being attacked by Egyptian or Hittite mercenaries, and so they fled for their lives.