Trying to retrieve Iphoto library

I recently had my hard drive replaced (along with many other components due to liquid damage). I had backed everything up with Time Machine the day before so I was under the assumption everything had saved. When I plugged in my external hard drive, everything returned EXCEPT all of my pictures! We can not locate an Iphoto Library anywhere on the backup. I have taken it to the Apple store and they also can't find the files. However, looking back, I don't believe there was ever an Iphoto Library folder saved in the Pictures file. (Being somewhat new to Mac, maybe I didn't have a true understanding of Iphoto). If all of my pictures were uploaded to Iphoto, wouldn't they have to be on my harddrive somewhere???? Is it possible the files are located somewhere else??? I had thousands of pictures and a completed 100 page book ready to order. Can anyone provide any advice on how I can retrieve these pictures??? I'm devastated! Thanks!