Would someone really trust Yahoo/Flickr to all their images and not have backups? Hopefully they didn't really care much about the images, else they should have copies elsewhere.
Anyway, the artist has originals backed up, but the article points out that all of the links to those images, and embeds, are now broken.
If URL is constructed from the data somehow (auto-slug from the title, hash or something), such restoration becomes way simpler
I am forced to conclude that few read the article, since most of the comments have focused on the - erroneous - idea that he depended on Flickr to store his data and had no backups.
It's a paid service[1]. So yes.
[1] he had a pro account.
(Point being, nothing site-wide in my quick glance seems to indicate a promise of the integrity and forever-ness of your data.)
That said, I can't seem to find it now. Weird.
What isn't backupable, and thus is lost forever is all of the comments he had on the various pictures, all of the groups his pictures belonged to, all of the embed's of pictures on various sites, all of the social aspect of Flickr (such as friends, family, all of those things).
I use Flickr to share my photos with the world, but I keep a local copy of all of my pictures on my local file server and on my laptop and all of the backups I have of that laptop...
1. people who've been in the situation of lost data when somebody else responsible for its backup hadn't backed the data up.
2. people who don't belong to the first group.
After graduating from the second group into the first, i've always been classifying my data as either "can loose, fnack it" or "i'm backing it up myself, right now"