Sorry for the delayed response. I did encountered the similar issue very late, hence thought of sharing the same.
You might not seen in WebI or in IDT preview and that is because you might not have set the level correctly while assigning the Hierarchy LOV. If you set the same at first level, then you won't see them in hierarchy, where as if you set is next level or next of next or last, then you should be able to see them in hierarchy.
Regards
Selva