Eric -- Yes, I'm sorry, but I'm not sure why it's showing in your app. We're looking into it further. In the meantime, if you want to manually hide the embed bar you can add the URL parameter &classicembedmode to the end of the URL.
Also, as noted in this article, &embed doesn't have any effect in Map Journal, so you can remove that URL parameter from your embedded story.
Owen Evans
Lead Product Engineer | StoryMaps