lost .iba file only .ibook file

I was working on an ibook and I had my almost finished version completed as an .ibook file. I lost my .iba file and now only have the .ibook preview I had completed. Is there any "easy" way of going back to an .iba file ? I have my assets (videos/pics) but the file names don't tell me much, I am not sure if there is a directory within the .ibook file that tells you where each file goes in respect to the books contents.