Observe Sally; she has found in a box in the attic a key. After holding the cold metal in her hand, it taking on her own ambient temperature, she considered the familiarity of the object. Its shape and weight. The strangeness of its teeth as opposed to other keys. Then it struck her. The shape of the reset port on her government-issued blinders.
She rushed down the ladder and into the bathroom to stare into the mirror. Sure enough there in the middle of her forehead was the hold. It was exactly the shape of the teeth of the key. She slid the key into it and twisted. The blinders fell from her face. She had not forgotten, it was always there.