What happens to equipment attached to a creature that becomes a non-creature permanent?

State-based actions (CR 704) are the game's automatic cleanup rules checked continuously. CR 704.5p specifically states that if an Equipment is attached to a permanent that is not a creature, the Equipment becomes unattached from that permanent. This happens the moment the permanent loses its creature type or creature card type.

The Equipment does not go to the graveyard or anywhere else — it simply becomes unattached and remains on the battlefield as its own permanent. It is now just sitting there, not equipping anything, until its controller pays its Equip cost again or some other effect attaches it.

Note that the Equipment's controller can choose to pay the Equip cost later (at sorcery speed, on their turn) to re-attach it to a valid creature. Until then, it grants no bonuses to anything.

Concrete example: Your opponent controls a Darksteel Citadel that has been animated into a 4/4 artifact creature with a Colossus Hammer attached. At end of turn, the animation effect wears off and Darksteel Citadel becomes a non-creature artifact land again. State-based actions immediately cause the Hammer to become unattached — it stays on the battlefield under your opponent's control but equips nothing.

This rule also applies to Fortifications attached to non-land permanents (CR 704.5q), following the same logic as Equipment and creatures.