When something is there one minute and gone the next, you can describe its disappearance as a vanishing.
Magicians practice long and hard to pull off the trick they call vanishing, while the art of vanishing seems to come easily to cats. Any time something — or someone — disappears mysteriously, it's a vanishing. The word vanishing is a gerund, or a noun that's made by adding ing to a verb, in this case vanish. It in turn comes from the Latin evanescere, "disappear," whose root word is vanus, or "empty."