Directional Light missing when changing scenes

I made a basic Unity scene with a character (mainScene) and then another scene with a UI button (menuScene) so that when I press this button in menuScene, the mainScene is loaded:

public void startSimulation()
{
    Application.LoadLevel("mainScene");
}

The mainScene has a directional light that is always there by default, but when I press the button in Editor mode, mainScene loads in a dark state. This does not happen when I build…

What am I missing or doing wrong?

This is a known bug that still persists in version 5.1.1f1

http://forum.unity3d.com/threads/application-loadlevel-application-loadedlevel-resets-level-but-causes-light-intensity-to-change.308248/