self topper. seen many. haven't seen many survive as they tend to do it young. almost always cause by a leaf eating insect. a stem with no nodal growth and only fan leaves can live for months, but without an apical top, it will never 'grow out of it' as there is nothing there TO grow.
you seem to have a lucky one. if it grows apically from the nodes below, it will grow and bush out. if not, it will eventually die.