Extended Tracked

Hi, i need help. I use unity2018.2.12f1&Vuforia 7.5.26. My task - dont hide object, after image doesnt in FOV. I made track device pose, positional mode, optimize for images and deleted code OnTrackingLost(). It works incorect. When status is NOT_FOUND camera does not see the model but model did not dissappaer. You can watch that in video