Spotlight would also have to read the AlbumData.xmo dB file and fix the location of all photos with that keyword from the data contained in it. That's not what Spotlight is designed to do. It searches by file name and file content. It will find the AblumData.xml file when searching for a title or keyword. If you write the keywords or titles back to the original files, as described in
Tutorial #1 Spotlight can pinpoint the location of all image files associated with a give keyword.
As it is now, Spotlight can find photos by file name of the original file. I don't see it getting tweaked so that it can read and interpret the xml file for the location of files associated with a given keyword or title. The majority of the customer base just don't need that capability.
TIP:
For insurance against the iPhoto database corruption that many users have experienced I recommend making a backup copy of the Library6.iPhoto database file and keep it current. If problems crop up where iPhoto suddenly can't see any photos or thinks there are no photos in the library, replacing the working Library6.iPhoto file with the backup will often get the library back. By keeping it current I mean backup after each import and/or any serious editing or work on books, slideshows, calendars, cards, etc. That insures that if a problem pops up and you do need to replace the database file, you'll retain all those efforts. It doesn't take long to make the backup and it's good insurance.
I've created an Automator workflow application (requires Tiger), iPhoto dB File Backup, that will copy the selected Library6.iPhoto file from your iPhoto Library folder to the Pictures folder, replacing any previous version of it. It's compatible with iPhoto 08 libraries and Leopard. iPhoto does not have to be closed to run the application, just idle. You can download it at Toad's Cellar. Be sure to read the Read Me pdf file.