Many orphans are not orphans
Children living in orphanages in Haiti are often not orphans but are instead temporarily housed there by their families because they expect their child will be better cared for in material terms than they would be at home. Parents take their children there on the condition that they can collect them again when they want to. In many cases, their trust is betrayed. You can read stories about orphanages and children in Haiti here (UNICEF and Bettercare Network) (in Dutch)
Adoption without consent
In the past, many children disappeared abroad for adoption without the consent of their parents. And it is still happening.
And sometimes in the West (e.g. in the Netherlands), insufficient checks are carried out to make sure that the files really are in order. Read "The interests of a child are rarely served by adoption" (UNICEF) (in Dutch).