Newly placed actor unloads after playing in editor once

The actor placed in the level will be unloaded after play in editor.  Without save the level (repro step4), the actor is not unloaded and show in editor.

1. Create new project with ThirdPersonExample.
2. Open in editor.
3. Place Cube using place actor tool.
4. Save level.
5. Play in editor.
6. Quit PIE.
7. See the outliner.

Result:

Cube actor is unloaded.

Expected:

Cube actor is loaded.