Particle System not playing? Unity 4.5

Could someone help me with the following? Play() doesn't start the particle system. The log outputs true for dustSteps.isStopped and false for isPlaying. The particle system has playOnAwake set to true. The particle system isn't attached to the game object as a component but is a prefab that is dragged onto the dustSteps variable in the inspector.

public ParticleSystem dustSteps;

 void Start () {

     if (dustSteps != null)
         Debug.Log ("dust not empty");

     dustSteps.Play ();
     dustSteps.enableEmission = true;

     Debug.Log ("Stopped? " + dustSteps.isStopped);
     Debug.Log ("Playing at start: " + dustSteps.isPlaying);
 }

Using Instantiate will create and play the particle system but you only seem to be able to assign what you instantiate to an Object, not GameObject so I cannot access everything needed.

I've searched this quite a lot and any tutorial videos just use Instantiate in the scripting.

Thanks very much for any help.