"Vanish into thin air" is a common phrase that is used to describe something that disappears or ceases to exist. However, there are several synonyms that can be used in place of this phrase. Some of these synonyms include "disappear without a trace," "evaporate," "dissolve," "cease to be," "vanish without a trace," and "fade away." These synonyms may be used to describe a wide range of things, from a person who suddenly disappears to memories that seem to disappear over time. Regardless of the context, these synonyms are effective in communicating the idea of something disappearing or ceasing to exist.