Ah right, The best way to solve this problem is to deactivate your GUITexture when tracking is lost, and re-activate when it’s found.
Alternatively you could use raycasting to check if you hit the plane object and change the plane layer to IgnoreRaycast when tracking is lost etc.
The easiest way to do this is in the DefaultTrackableEventHandler.cs script.
You should have the functions OnTrackingFound() and OnTrackingLost(), you can use these to activate and deactivate, which should fix your problem
The issue you are having is that when you lose tracking, QCAR cannot sync it’s ‘real camera’ with the game camera, so it just leaves the game camera where it is, by default it disables the renderers for all the objects that it loses track of, and your script basically over-rides that, which is why the teapot appears on screen
Unfortunately I can’t right now as I am at work, but it shouldn’t be too difficult given what you have there.
You basically just need to change that isTracking boolean to true in OnTrackingFound() and to false in OnTrackingLost()