selecting source menu missing

I’m trying out the official iPhone remote app. Looks pretty amazing so far. When trying to open a movie(not using the button GUI with the up/down/left/right), I get all the way through the movie selection and it reflects fine on the tv as well but then I select my movie, the tv displays the list of all possible sources but my phone doesn’t. How do you select the source? Do I then have to switch back to the button remote GUI?