If Faith Unbroken leaves the battlefield before its triggered ability resolves, the targeted creature won't be exiled.

Auras attached to the exiled creature will be put into their owners' graveyards. Any Equipment will become unattached and remain on the battlefield. Any counters on the exiled permanent will cease to exist.

If a token is exiled, it ceases to exist. It won't be returned to the battlefield.

The exiled card returns to the battlefield immediately after Faith Unbroken leaves the battlefield. Nothing happens between the two events, including state-based actions. However, if the creature Faith Unbroken enchants leaves the battlefield, Faith Unbroken won't leave itself until state-based actions are checked.

In a multiplayer game, if Faith Unbroken's owner leaves the game, the exiled card will return to the battlefield. Because the one-shot effect that returns the card isn't an ability that goes on the stack, it won't cease to exist along with the leaving player's spells and abilities on the stack.