Keywords: undetectable, invisible, disappear, missing, disappearance
As a Noun
1. The situation in which a thing or a person cannot be found and nobody knows where they have gone or where they have been taken to. English = disappearance.
As a Verb or Adjective
1. Of a thing or person, to be unable to be seen because it (or he or she) has gone away or been taken away unexpectedly or has been lost. English = disappear, (be) missing.
2. Of a thing or person, to be unable to be seen because it has gone away, is hidden, or is invisible. English = (be) undetectable, (be) invisible.