온데간데 없다 (on-de-gan-de oeb-da) – disappeared from sight/vanished into thin air
This phrase is an exaggeration of 없다 or 안 보이다.
I’m not very sure how to explain this phrase but you can look at it this way:
온데 = came but
간데 = went but
없다 = there isn’t (anything)
In a sense, you came here, searched, went there, searched, but there isn’t anything. If something has disappeared from sight or vanished into thin air, you won’t be able to see anything no matter how much you searched.
Just like 없다, this phrase acts as a verb.
그 친구가 나 봤는데 한 마다도 말하지 않고 온데간데 없어서 정말 싫어.
That friend saw me but he didn’t even say a word and disappeared from sight so I really dislike him.
황 선생님은 가르칠 때 자주 핸드폰 게임을 해서 선생님에 대한 존경이 온데간데 없어.
Teacher Hwang frequently plays mobile games while teaching so our respect for him vanished into thin air.