How do I fix missing and corrupted images after update to Mountain Lion 10.8.2 and Aperture 3.4?

Question

Last night I tried to update to Aperture 3.4 on my MacBook Pro (late 2007 / 3,1 model) and received a message that I needed to install Mountain Lion 10.8.2 first.  However, there was no update in my App Store account for 10.8.2.  The update for 10.8.2 appeared above the Aperture 3.4 update after I restarted the laptop and rechecked for updates.  I proceeded to update Mountain Lion and then Aperture.  Everything seemed to be working fine so I opened Aperture 3.4 and watched it update the database without any issues...
Upon examining the small library (of approximately 1200 images totaling about 8 GB) that I leave on this MacBook Pro specifically for testing Aperture updates, I observed the following:
I know anything can happen with stored images, so I try to create redundancy by duplicating important photos on import to an external device, running Time Machine backups and keeping memory cards stored away until I am comfortable with the integrity of the first 2 methods.  I am not really worried about this specific Aperture Library on this laptop because it has become my "laboratory" for testing new updates before we apply them to our other computers.
In general, I try not to be too early of an adopter when it comes to software and updates--even though I have had remarkably few problems with Apple updates in the past.  However, my success rate with Apple's products and "feature curiosity" occasionally leads me to update early!  It is my curiosity that, again, has me wondering:  What went wrong and how can I fix this in case it happens to something important in the future?

Answer 1

I still don't know what happened to my test Aperture Library after the update to 3.4...Not only were my previews lost, but so were the original images!  Needless to say, I haven't bothered to update the main library on the Mac Pro because I don't want to deal with this level of uncertainty (even with backups in place).