Focusing on speed:
* He disappeared like a puff of smoke in the wind.
* She vanished like a drop of water in a hot pan.
* The car sped away like a ghost in the night.
Focusing on stealth:
* He slipped away like a shadow in the moonlight.
* She faded into the crowd like a whisper in a storm.
* The thief disappeared like a chameleon blending into its surroundings.
Focusing on the unexpected:
* He vanished like a dream fading at dawn.
* She disappeared like a bubble popping in the air.
* The opportunity slipped away like sand through your fingers.
Focusing on the absence:
* He was gone like a memory fading in the past.
* She disappeared like a star swallowed by the night.
* The sound of the music faded away like a whisper on the wind.
Remember to choose the simile that best fits the context and conveys the desired emotion or effect.