My children's great-great-grandfather apparently disappeared around 1920. In a renewed attempt to find him, I have decided to look for him in areas where he had siblings, aunts, uncles or cousins. Some of his immediate family was in the Chicago, Illinois, area, but research on his parents indicates he had uncles and aunts in Texas and Canada--two places he could easily have settled.
So when someone "disappears" don't go "nationwide" until you have to. Keep in mind that they might have settled, even temporarily, near a member of their extended family.