How to anchor GameObject on environment using Vuforia device tracking markerless?

I’m using unity and vuforia and I have similar project to this video: Unity réalité Augmentée avec Vuforia - Device Tracking - YouTube.

Is it possible to resolve the problem at 7:46? I want to walk towards the object and that it does not move so that I can go through it.

I can do this when I use ground plane but I don’t want to place the object on the floor but place it in a random position 360 degrees around me.

U find a solution?