I feel sorry for the person, but if the photos are truly important and irreplaceable they should have been following the 3-2-1 rule.
At least three copies, in at least two physical locations, at least one of which is offline.
If you are storing any digital data in one single place, no matter how trustworthy and reliable that single place may seem to be, you're at risk of losing it. Most people learn this lesson the hard way, unfortunately.
distibuted testing systems or whatever they call it are often based on a hidden setting in your cookies/cache, and may have undesired effects. Clearing them gives you another value for the setting, which means you will not be using the breaking behaviour of the previous trial. Its an easy way to keep the fact that you're in a possibly unstable environment away from the user.
Just a wild guess but perhaps there were errors in the upload/backup process that went unnoticed. Then when the originals were deleted to save space, the user lost them.
Something related happened to me. Some of the photos on my google photos are just completely black. It's not exactly the same because this guy's photos are "corrupted". Mine are just literally black. Not all of them, just around 20, all in the same day, all in sequence.
At least three copies, in at least two physical locations, at least one of which is offline.
If you are storing any digital data in one single place, no matter how trustworthy and reliable that single place may seem to be, you're at risk of losing it. Most people learn this lesson the hard way, unfortunately.