it's been a long time since you posted this - I posted the same problem a few days ago, but now found the place where my photos went hiding.
So, everybody who has this problem:
Look at your finder window and see on the left menu column under "search for" some folders named "all images", "all movies" and "all documents".
If you open "all images" you will find literally ALL the images you ever brought into your computer and some weird sequence, probably by date of import.
It's a tedious job to work through tens of thousands of images, but there they are.
So, nothing is lost, but please APPLE people, there IS a bug in iPhoto which needs fixing!!!
We're not used to bugs with our Macs...
Download and use Find Any File to search for a file named "Library6.iPhoto". It's a file that exists in every iPhoto library regardless of what the library has been named. If you find more than one you can open them to see if the other library has your photos.
If there is only one library make a temporary, backup copy (if you don't already have a backup copy) of the library and apply the two fixes below in order as needed:
Launch iPhoto with the Command+Option keys held down and rebuild the library.
Select the options identified in the screenshot.
Using iPhoto Library Manager to Rebuild Your iPhoto Library
- Download iPhoto Library Manager and launch.
- Click on the Add Library button, navigate to your Home/Pictures folder and select your iPhoto Library folder.
- Now that the library is listed in the left hand pane of iPLM, click on your library and go to the File ➙ Rebuild Library menu option
- In the next window name the new library and select the location you want it to be placed.
- Click on the Create button.
Note: This creates a new library based on the LIbraryData.xml file in the library and will recover Events, Albums, keywords, titles and comments but not books, calendars or slideshows. The original library will be left untouched for further attempts at fixing the problem or in case the rebuilt library is not satisfactory.