Set iPhoto to photo folder on external hard drive, iPhoto cannot find photos

A year ago I used a folder on an external drive as my iPhoto library. I went on a trip and used another library in my Pictures folder, so now I have two libraries and want to merge them.

However, now I open iPhoto, click "Switch to Library", select the external hard drive library, and iPhoto thinks there are no photos there – I get the "To get started with iPhoto" post-it note in the background, and there are no photos, events, etc.

I am running iPhoto 9.5.1 (902.17). I have a folder called photos with the following contents:

-rw-r--r--@  1 kevin  staff    16B Jul 20  2011 .ipspot_update
-rw-r--r--@  1 kevin  staff   2.0K Jul 10 21:10 AlbumData.xml
drwxr-xr-x   2 kevin  staff    68B Jul 10 20:19 Attachments
drwxr-xr-x   2 kevin  staff    68B Dec 21  2010 Auto Import
drwxr-xr-x   3 kevin  staff   102B Dec 21  2010 Contents
drwxr-xr-x   3 kevin  staff   102B Apr 25  2011 Data
drwxr-xr-x  20 kevin  staff   680B Jul 10 21:10 Database
-rw-r--r--@  1 kevin  staff   324B Jul 10 20:19 Info.plist
-rw-r--r--   1 kevin  staff    20B Dec 21  2010 Library.data
-rw-r--r--   1 kevin  staff    20B Dec 21  2010 Library.iPhoto
-rw-r--r--   1 kevin  staff   5.4K Apr 25  2011 Library6.iPhoto
drwxr-xr-x   2 kevin  staff    68B Jul 10 20:19 Masters
drwxr-xr-x   3 kevin  staff   102B Apr 25  2011 Modified
drwxr-xr-x   3 kevin  staff   102B Apr 25  2011 Originals
drwxr-xr-x   2 kevin  staff    68B Jul 10 20:19 Previews
-rw-r--r--@  1 kevin  staff   341B Jul 10 20:19 ProjectDBVersion.plist
-rw-r--r--@  1 kevin  staff   576K Jul 10 21:10 Projects.db
-rw-r--r--@  1 kevin  staff    11M Dec 21  2010 ThemeCache
drwxr-xr-x   3 kevin  staff   102B Jul 10 20:19 Thumbnails
drwxr-xr-x   4 kevin  staff   136B Jul 10 21:10 iLifeShared
drwxr-xr-x@ 25 kevin  staff   850B Jul 10 21:09 iPhoto Library
-rw-r--r--@  1 kevin  staff    35B Apr 25  2011 iPhoto.ipspot
-rw-r--r--@  1 kevin  staff     1B Jul 10 21:10 iPhotoLock.data
drwxr-xr-x@  3 kevin  staff   102B Apr 26  2011 iPod Photo Cache

Info.plist contains the following:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>CFBundleGetInfoString</key>
    <string>iPhoto Library 9.5.1</string>
    <key>CFBundleShortVersionString</key>
    <string>9.5.1</string>
</dict>
</plist>

Inside the iPhoto Library, I have the following:

-rw-r--r--@  1 kevin  staff    16B Jan 25 14:30 .ipspot_update
-rw-r--r--@  1 kevin  staff   2.0K Jul 10 21:05 AlbumData.xml
drwxr-xr-x   2 kevin  staff    68B Jul 10 20:18 Attachments
drwxr-xr-x   2 kevin  staff    68B Apr 23  2009 Auto Import
drwxr-xr-x   3 kevin  staff   102B Apr 23  2009 Contents
drwxr-xr-x  12 kevin  staff   408B Jan 25 13:40 Data
drwxr-xr-x  20 kevin  staff   680B Jul 10 21:09 Database
-rw-r--r--@  1 kevin  staff   324B Jul 10 20:18 Info.plist
-rw-r--r--   1 kevin  staff    20B Apr 23  2009 Library.data
-rw-r--r--   1 kevin  staff    20B Apr 23  2009 Library.iPhoto
-rw-r--r--   1 kevin  staff   6.8M Jan 25 14:26 Library6.iPhoto
drwxr-xr-x   2 kevin  staff    68B Jul 10 20:18 Masters
drwxr-xr-x  10 kevin  staff   340B Jan 25 13:47 Modified
drwxr-xr-x  12 kevin  staff   408B Jan 25 13:40 Originals
drwxr-xr-x   2 kevin  staff    68B Jul 10 20:18 Previews
-rw-r--r--@  1 kevin  staff   341B Jul 10 20:18 ProjectDBVersion.plist
-rw-r--r--@  1 kevin  staff   576K Jul 10 21:09 Projects.db
-rw-r--r--@  1 kevin  staff   7.5M Apr 23  2009 ThemeCache
drwxr-xr-x   3 kevin  staff   102B Jul 10 20:18 Thumbnails
drwxr-xr-x   4 kevin  staff   136B Jul 10 21:05 iLifeShared
-rw-r--r--@  1 kevin  staff    50B Jan 25 14:26 iPhoto.ipspot
-rw-r--r--@  1 kevin  staff     1B Jul 10 21:09 iPhotoLock.data
drwxr-xr-x@ 56 kevin  staff   1.9K Jan 25 14:28 iPod Photo Cache

I checked the Console and didn't find any messages from iPhoto in there.

I opened Database/Library.apdb in both the folder and the subfolder, and the RKMaster table seems to believe that there are no photos in my library (no rows in the table), however the Originals and the Modified folders have tons of photos there.

Any theories about why iPhoto can't find my photos? I have made backups of everything, so feel free to suggest destructive actions.