lost data

Please explain how your folder "has disappeared."  

As Glenn has said, the Organizer only retains low resolution thumbnails of your photos.  Depending on your needs, if the original photos have been truly and permanently deleted from your hard drive, you can take a screenshot of each thumbnail to "recover" them.

Have you performed a Search of your computer to find the missing folder?  As Glenn says, folders can often be moved unintentionally.  I use a free utility called Everything which is far better than a Windows search for finding files and folders.

The pictures in organizer are just thumbnails of the images.   Folders generally don't vanish, it's easy to move them them into another subdirectory of something if you are not paying attention.

Bottom line: with the folder "gone" you are basically out of luck, unless you did a complete (including the images) backup from within organizer. 

Please check your recycle bin and see if the folder is there. 

A folder has gone missing from my hard drive, but it still exists in the organizer, imported 2 years ago. Can I go backwards to recover the photos? I tried looking for earlier versions of Pictures, but none were found.