title: Can not get when the device tracking is lost
body: <p>Hi guys i want to compare some Augmented reality SDKs for my research. I have checked ARCore and with ARCore you can check when the tracking is lost. I am trying to do same with Vuforia. I have a game with an input scene like this:
   <a href="https://i.stack.imgur.com/meRNW.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/meRNW.png" alt="enter image description here"></a></p>
  
  <p>where you choose FusionProvideType and when you press the button mainscene is loaded where i assign the selected dropdown option to <code>DeviceTrackerARController.Instance.FusionProvider</code> And then i load main scene. 
  Main scene Looks like this:<a href="https://i.stack.imgur.com/5mPnG.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5mPnG.png" alt="enter image description here"></a> </p>
  
  <p>In red i have the position of ARCamera and orange has <code>TrackableBehavior.currentstatus</code> of my astranaut image target. 
  I have tried all the fusion types but what i dont understand is when i use <code>VUFORIA_VISION_ONLY</code>, <code>VUFORIA_SENSOR_FUSION</code> and  <code>OPTIMIZE_MODEL_TARGETS_AND_SMART_TERRAIN</code> and lost tracking, i can recover device position by moving device away from the surface without going back to marker. So even if marker is not visible in the videoframe the device position gets recovered and keeps getting updated. But <code>CurrentStatus</code> stays undefined which i expect it to be <code>EXTENDED_TRACKED</code>. My question is how can i inform user when the tracking is lost using Vuforia since i can not use <code>CurrentStatus</code>, <code>Status</code> or <code>StatusInfo</code> from <code>TrackableBehavior</code>. Thanks in advance.</p>