Book module - all pages lot

I have been working on a book of about 120 pages, and suddenly all the pages and content have disappeared.  I'm left with just a few blank pages , similar to when you start a new book.

I don't understand what has happened.  On the LH side in the Collections panel, the collection is stil there, and as the book name shows as a sub collection with a book icon next to it.  In the film strip, all the photos I used have a 1 over them.  Surely this shows that the pages still exist somewere?

In another thread, I read to click on the 2 icon in the filmstrip.  But this opens a new window with just the selected photo.  Wthin the same collection, a different version of the book remains intact.  

 I have tried opening an old version of the catalogue and that didn't help.  I'm certain that I didn't delete any pages, I feel that I must have switched the view or mis-clicked something, I was working on the cover at the time,

Grateful for help in recovering my pages.