If you are using variables from a Bolt Scene class, they are visable in the heirarcy, when in play mode. If you select a game object in the Hierarchy before entering playmode, this will block the generation of the scene variable container.

Video Attached.
[^SceneVariablesLostWhenGameObjectSelected.mp4]

Steps to reproduce
* Open Bolt 2.0.0.a12 with Unity 2019.4.0f.
* Create a Bolt Class and add it as a component to a game object.
* Add a Flow Graph to the class.
* Open the Flow Graph.
* In the project palette, create a Bolt Class but change the scope via the inspector to Scene.
* Add a String variable to the class and give it a value.
* Open your Flow graph.
* Add a debug.log to your graph.
* As it's input add the Scene Class string variable by dragging and droping it from the Bolt Explorer.
* Play the scene. Notice the creation of a scene variable container in the Hierarchy.
* Stop the scene and select a game object in the Hierarchy.
* Play the scene again
Notice issue >> The scene variable container is not created.

Tested Broken: 2019.4.0f1, 2.0.0a12
Tested Working: 2019.3.15f1, 2.0.0a10