Is first one incorrect? If so, then and why there should be to? And what respond would be?
Where did you disappear?
Where did you disappear to?
Is first one incorrect? If so, then and why there should be to? And what respond would be?
Where did you disappear?
Where did you disappear to?
Answer: He disappeared in the woods.
Answer: I went out jogging
disappear to is used in colloquial spoken language to mean: go, when it seems that a person has "disappeared". Indeed, they have disappeared from the view of the speaker.