A face-down creature is still a permanent on the battlefield — it is simply a 2/2 creature with no name, types, or abilities. When it is turned face-up via morph, it does not leave the battlefield and return; it simply changes its characteristics in place. Because it is the same object, anything attached to it stays attached.
This is confirmed by CR 701.33e (turning a face-down permanent face up) and the general rule in CR 303.4f, which states that an Aura's attachment is not affected by changes to the enchanted permanent's characteristics. The permanent's identity on the battlefield is continuous, so attachments persist.
One nuance: after the creature turns face-up, the Aura's enchant condition is re-evaluated. If the newly revealed creature has protection from the Aura's color or another effect makes it an illegal target, the Aura would be put into its owner's graveyard as a state-based action (CR 704.5n). But if the enchanted permanent is still a legal target, the Aura stays.
Example: Your opponent plays a face-down morph creature and you cast Pacifism on it, preventing it from attacking or blocking. When your opponent flips it face-up revealing Exalted Angel, Pacifism remains attached — the Angel still cannot attack or block, unless Pacifism becomes illegal to have on it (e.g., if the Angel had protection from white).
Unofficial fan resource — not affiliated with or endorsed by Wizards of the Coast. Answers are AI-generated estimates grounded in the Comprehensive Rules and are not a substitute for an official judge. Verify anything match-critical.