This is a very trivial demo that creates a single copy of a LevelManager object, which can save information between Scene/Level changes. I’m putting it here for an Unity Answers post, since I don’t see a way to upload files there. 
John C>
I downloaded your demo, after having closed out of Unity. When I rebooted Unity, my most recent project loaded and your demo had erased (and replaced?) my terrain.
I post this as a warning to other, potential users.
I would recommend to create a blank project so you can avoid having problems in your own.