Not sure what you mean - do you mean they disappear if you, say, move the camera or point of view? If so this is expected, as Displacement is calculated based on what is visible in the view at the time of starting IR - this is Screen mode, where things not in the field of view do not get displacement calculated, to speed up calculation and reduce memory requirements, and this means if you move the camera you may find objects where displacement has not been calculated. IR would need to be restarted in this case (or you can use World mode rather than Screen, but then you lose the benefit of faster calculations and reduction in memory needs).