Am I the only one who sees this crucial flaw?

Rating: 6/10 (1 October 2009)

This film is very pretty, subdued, and haunting, like everyone else says, but it has a major plot flaw that spoiled it for me.
SPOILER BEGINS HERE: The mother was supposedly raised in this orphanage, right? And those 5 children were her playmates. Yet, she doesn't remember her playmates all suddenly VANISHING, while they were still children? Wouldn't there have been a big scandal or mystery as to where the children went? And that woman that poisoned them - the mother doesn't even remember her working at the orphanage (she is told that the woman only worked there a short time.) Gee, wouldn't somebody have wondered why this woman suddenly left, after 5 children vanished? It seems to me the mother would have said, when her child vanished, "Gosh,this is just like when I was a child - 5 of my playmates suddenly vanished from this orphanage!" We know the children were not believed to have died, or died from natural causes, because the woman Benigna took the bodies, hid them, and sealed them up. But no mention is made of anyone ever having even noticed they were gone. And I am sure the mother, at least would have been traumatized by losing so many friends at once.
There are people that remember the little boy, Tomas, drowning in the cave when the other children took his mask. But nobody remembers the other children vanishing? Did I miss something here? There are seemingly hundreds of rave reviews for this movie, and nobody seems to have noticed this gaping hole in the plot but me? I must be missing something...
END OF SPOILER It was a nice, subdued ghost story, but I like everything to make sense on some level.