That's because importing from another iPhoto Library folder isn't the way to restore an iPhoto Library. I'm surprised you were able to do it without a bunch of warning dialogs.
If you still have the original iPhoto Library folder intact, the thing to do is restore it as I've described earlier. If you have sufficient disk space, quit iPhoto and drag the existing iPhoto Library folder from Pictures to the desktop. Then drag your backup iPhoto Library folder to the Pictures folder, and the only thing left to do is to start iPhoto. If all's well, move the desktop copy of the iPhoto Library folder to the trash, then empty the trash.