disappearance-n; 2 Senses

Sense Number 1: something in a state of unknown location

Commentary: DISAPPEARANCE[+state][+location][+unknown]
NOTE: implies the object is not visible, it's whereabouts are unknown, but it is assumed to exist somewhere.

The police are investigating the woman's disappearance.
The museum is offering a reward for any information regarding the disappearance of their Piero della Francesca pieces.
The cat showed up at its home after a four-day disappearance.
The disappearance of the rabbit down a hole intrigued Alice.

WordNet 3.0 Sense Numbers: 1, 2

Sense Number 2: a state of no longer existing

Commentary: DISAPPEARANCE[+state][-existence]
NOTE: implies the object no longer exists.

He regretted the disappearance of Greek from school curricula.
They are concerned about the disappearance of much of the rain forest.
Mary marveled at the disappearance of the stain from the white fabric.
The new treatment resulted in a total disappearance of the tumor.

WordNet 3.0 Sense Numbers: 3, 4