Camera 3D tracker make the object disappear

Carefully re-read what I wrote in the first reply. 

When you run the camera tracker and create your first Camera and Track Solid the track solid is at 0, 0, 0, not at the comp center (960, 540 for an HD comp) and the camera is pointing at the center of the solid. Move up or down the timeline and the Track Solid, Your purple layer 2,  does not move but the camera does. 

If you select any of your 3D text layers and hold down the Shift key and parent the text layer to the Track Solid the 3D text layer will snap to the same position and be visible in your comp panel.

You will not have very much success learning how to use After Effects unless you take some time to study some good tutorials. I already pointed you to the User Guide. You need to study the 3D workspace and learn about the UI. If you change your comp panel to 4 views you will see that the Track Solid is in the top left corner of the comp, the camera is pointing at it, and the 3D text layers you created are at the comp center completely out of the camera's view. The only reason that you are seeing the text in the front view is that the front view always looks directly down the Z-axis to the comp center.

Please spend some time learning how to use the Camera Tracker. Even most of the poorly produced and poorly thought out Camera tracking tutorials produced by enthusiasts and posted on YouTube will show you how to get started with camera tracking.

You have added a track solid and some track nulls. Preferrable the solid you added would be set to the origin and ground plane of the shot. None of those layers are labeled so there is no way to know where they are and I don't see any of them in the frame. 

A new layer is always at Comp Center, but the camera is not pointing at Comp Center. To bring your 3D text into view you need to scrub through the timeline until you find one of the Track Nulls or the Track Solid, hold down the Shift key and Parent the Text layer to the appropriate layer. Then you need to adjust the rotation of the text layer and position it properly in relation to the surface you have defined with the nulls or solids you placed in the scene. 

Spend some time with the User Guide. There is a 16 minute tutorial in the Experienced section that goes over the basics of the camera tracker. 

Screen shoot