this is a beautiful post and I found myself nodding over and over all the way through but it also highlights again the reason why I was so apprehensive about cat's idea of the 'imago'. The 'imago' word implies that what you saw in this little boy and the way in which you grew to love him was some sort of mirage which was bound to die when he became a teenager, but I just don't think that's how it is and I dont think that's what Cat meant. When we love someone as you loved this little boy we are allowed to see them as God sees them: it's as though He opens up a tiny window through which we are able to glimpse something of Himself through the life of another person and it is always difficult and painful because it takes us out of ourselves and opens up a world that pulls us completely out of our 'comfort zones' and renders us terribly vulnerable. We fight to close that window as quickly as possible because we get so wounded whilst it is still open.
But this is a glimpse of the life that God is calling us into: the life of an utterly vulnerable God no less where we too are called to allow ourselves to be vulnerable because we cannot touch others if we cannot allow ourselves to be touched.
What you loved in this little boy has not 'gone away' or 'died' it has just become hidden from you and now only God loves him again as I think only God loves all of us who are not loveable from the outside and, of course, you are called to go on loving him in faith even if he is absent from you and no longer interested in you.