Albert Barnes Commentary 1 Kings 20:41

"And he hasted, and took the headband away from his eyes; and the king of israel discerned him that he was of the prophets." — 1 Kings 20:41 (ASV)

He was of the prophets - Josephus and others conjecture that this prophet was Micaiah, the son of Imlah (but compare to 1 Kings 20:13).