Have you tried to "rebuild" your iPhoto? I had some photo loss a short while ago, and when I ran the "rebuild" nothing good happened. Then I ran the "manual" rebuild. Everything came back! Now, the instructions from Apple on how to do this state that there could be some duplication of files and loss of titles, comments, etc. and I did find this to be true. I have approximately 3,000 photos, and when the rebuild was done, I had 15,000. But, having the photos back was worth what I had to go through to retrieve what I wanted.
Good luck!