Mosiah 20:12

And it came to pass that they found the king of the Lamanites among the number of their dead; yet he was not dead, having been wounded and left upon the ground, so speedy was the flight of his people.

They found the king of the Lamanites among the dead bodies. But he was not dead. He was hurt and left on the ground. His people had run away too fast to get him.

After the battle, they found the Lamanite king among the dead—though he wasn’t actually dead. He’d been wounded and left behind when his army fled.