Missing originals from ibook

I have an external hard drive that belongs to a good friend with backups of photos a friend took from several years ago. Among the backups is an iphoto book she created for me. I want to take those images and copy them to my own desktop or a CD/flashdrive so I can print enlargements, but they aren't in the iphoto library at the appropriate date they were taken. Is there a way to retrieve them via the ibook itself or are they somehow in the library but hidden?