Do you mean when you create a page you are unable to find ‘Form Horizontal’ or ‘Form Vertical’ building blocks? If this is the case then please make sure you have these building blocks available in your Atlas_UI_Resources module > Forms folder > ‘Form_Horizontal_Edit’ and ‘Form_Vertical_Edit’. If these building blocks are not available in the specified location then you will not see anything while creating new page.
To get it back you download the latest Atlas-UI-Resources module (if you have not made any custom UI changes) else you can import required building block from your existing project.
Hope this helps!