To make matters far more difficult these children who do (allegedly) remember details don't volunteer them at such an age, generally; they may also need to be queried as to some specific image or object or name, which they can respond to. This is how Tibetan rebirths are allegedly "found"; they show the kid two sets of objects, one from the dead lama and one from somewhere else. The child who is the rebirth is expected to select only the implements from the dead lama