I've googled around and have tried several things to get the title bar to display when I install my app on my phone but it doesn't show. It shows when I'm developing the app in MIT but not when I deploy my app to my phone.
You will have to make your own title bar for a compiled apk, this bug is not yet resolved in Appinventor. You could also use a popup extension to replicate and enhance the three dots menu.
From what I saw in the repository, this will be fixed in the next version of app inventor.