Rule 359.3.e.4

If a target changes Zones to or from a Non-Board Zone and then returns to its original zone, it is no longer a legal target, because it's not treated as the same object. Examples: An enemy unit at a battlefield is no longer a legal target if it is no longer an enemy, no longer a unit, or no longer at a battlefield. A unit with 3 or less Might is no longer a legal target if it is no longer a unit or if its Might is greater than 3. Something that's exhausted is no longer a legal target if it is no longer exhausted. (It can't stop being "something.")