Can you tell us which folder you moved to the trash?
Do you know where you took the folder from?
If you moved the file back from the trash to your pictures folder then all we should ned to do is to get iPhoto to open and then rebuild your photo library.
So could you look in the HD / Users/Your Name / Library/ Preferences folder and find the com.apple.iphoto.plist file and trash it.
Once you have done that can you then launch iPhoto and let me know if it opens correctly then asks you to reindex or add photos, If it does can you point it to the correct location where your pictures are stored.
What version of iPhoto do you have?
Have you upgraded it recently?
If not can you drag the plist back from the trash to the HD / Users/Your Name / Library/ Preferences folder and then relunch iPhoto and let me know if it opens correctly.
Could you shut down iPhoto then re-open while holding opt+cmd+shift, You should get a message asking if you want to rebuild the iPhoto library which can take a little while.
Let me know what happens.
You need to perform option 3 which is to rebuild the iphoto library database.
If that does not work try option 4 if you moved th photos back to their original locations.
Sorry, I thought you were able to retrieve all of your photos and move them back to the original folder I did not realize you were missing some.
In that case we will need to retrieve your original photos before we can rebuild unless you dont need them.
Let me know
Again I am sorry, I was laboring under the wrong impressions so i am sorry I wasted your time so far.
What we need to do is try some form of undelete or format recovery software like Macintosh data recovery http://www.macintosh-data-recovery.com/ or Kernel http://www.datarecoverymac.com/ A free trial can be found at both of the links I provided.
If you download the trial version of the software to see if it can find your files you can then purchase the full version to recover your files for $129.00 or $149.00 and once you have recovered the folder and files you can just move it from the reovery location back to its original location and relaunch iPhoto and reindex.
Let me know if you need more info.
So what hapens if you reindex now?
If the photos will open from their location then could you Move the iPhoto Library Folder to the desktop and launch iPhoto.
It should ask if you wish to create a new Library, Say Yes.Go into the iPhoto Library Folder on your desktop and find the Originals folder. From the Originals folder drag thephotos to the iPhoto Window and it should recreate them in the new library.