I just noticed that my UWP app has "lost" its title bar. The minimize/maximize/exit buttons are there, but the main bar (along with app title) is invisible. It looks like it is overlayed by the main page of the app.
I was in the middle of trying to add a custom Hamburger menu to the title bar when I happened to notice this. I've since restored the xaml file back to the original but still the title bar has disappeared. Something simple and stupid, I'm sure but what?