Google Images and, by extension, all search engines suffer from a serious temporal problem that you don't hear much about. The gist of the problem is that an index of data is always out of sync with the data it indexes.

Think about it this way: Yesterday Google's faithful 'droid Googlebot popped over to this site and looked at what was on the home page. It made a copy for its own index and entered the page into its database tied to specific words it found on the site. Meanwhile, however, the site itself has changed - indeed, there's no way that Google (yet) knows about this new entry because it needs to come back and visit again.

So in microcosm I have the same problem you do: if people search Google for "image vanished from Google Images" they cannot find this article because Google doesn't know about it yet. Tomorrow, or perhaps a few days down the road, that'll change, but for right now, Google is out of sync with my site.

You're seeing the same problem in reverse: Google Images found a graphical element on a Web page, indexed it and added it to the Images database, and is showing a cached (e.g., saved on the Google server) copy of the image as part of the result of your search. Meanwhile, though, the site itself has changed and no longer contains that image.

The result: exactly what you are seeing, that you're getting a thumbnail and an indication that there's a lovely image that's a perfect match for your search, but the image no longer exists on that server.

It's frustrating, and what's worse, there's nothing you can really do about it other than shrug and look for an alternative image that will serve your purposes better.

At some point Google Images will flush its cache (great names we geeks have for these things, eh?) and recheck the site, finding at that point that the image has vanished and removing any trace of it from the Google archive. Until then, it's inevitable that other people will have a similarly frustrating experience.

Hope that clears things up!