Was the Prophet's knowledge (PBUH) in Medina of the martyrdom of the leaders of the Battle of Mu'tah (Zayd, then Ja'far, then Ibn Rawahah) part of the knowledge of the unseen, which only Allah knows, or was it through revelation?

The Prophet, peace and blessings be upon him, informed about the martyrdom of Zayd, Ja'far, and Ibn Rawahah in the Battle of Mu'tah before the news reached him. This is from the knowledge of the unseen which Allah revealed to him, in affirmation of His, the Almighty's, saying: "Say, 'None in the heavens and earth knows the unseen except Allah,'" and His saying: "Knower of the unseen, and He does not disclose His [knowledge of the] unseen to anyone, except to one whom He has approved of as a messenger."