To reproduce:

1. Open attached project.
2. Run tests.

Result:

Moving game object to scene (which was unloaded), on sceneUnloaded callback is possible. It succedes, then scene is destroyed but object is not unloaded, it stays without valid scene, floating in space. So if user looses reference to that game object, it won't be possible to destroy it.

Although, if unloaded scene does not have path (it means it come from SceneManager.CreateScene in runtime), then game object is stored in DontDestroyOnLoad scene

Expected result: I think gameObject.scene should always be valid. This operation should not be possible at all, or object should be stored in DontDestroyOnLoad.

Reproduced: 2017.2.0b3 (4c2ac554540c)