It gets moved to a separate scene on the mind map. But I've found for the game I imported the content of the scene keeps getting deleted.
Main menu has it's own "world" (blue node) when doing import. That may be what you are seeing. You should have another world which contains your gameplay. Not sure if that helps, but all the scenes should be there in some capacity. If not it might be helpful to email support for your specific situation.
@Andy I mentioned previously that I'd noticed the main menu scene getting deleted. Not sure if anyone else has reported it since, but I've just discovered when it happens. If I switch any of the scenes around within the game field scene (i.e. drag one scene tab to a different position) anything on the main menu scene gets deleted. If no one else has reported it or you're unable to recreate the issue and need me to submit to support let me know.