If you can get to the setting Cog in another screen, then tap on it. Scroll down to Interface Options/ Edit Bottom Menu. There you can enable/disable the different icons for the bottom of the map screen.
Not sure what you mean by the “Lock button”, unless you mean “Exit”. Joao explained to me when I asked about that, that it would not be smart to put the Exit button on the map screen. So the fact that you’re not seeing nor can put it on there is not a flaw, it’s by design.
