If people or things disappear, they go somewhere where they cannot be seen or found:
The search was called off for the sailors who disappeared in the storm.
I can't find my keys anywhere - they've completely disappeared.
The sun disappeared behind a cloud.
We looked for her but she had disappeared into the crowd.
The movie is about a girl who mysteriously disappeared while on a picnic at Hanging Rock.
I don't know how it's possible for a person to disappear without trace.