You ever see "supplemental result" tagged on to a result found within the Google index? What it means is that this version of the page is no longer found on the Web, and only once existed in the past, which Google has captured and stored in its index. A thread at WebmasterWorld leads into what really is a supplemental result, and if you look at msg #13 you will see an excellent observation. In short, supplemental results can occur on the keyword phrase level. For example, if page A is listed in Google, it can be found with and without the supplemental result line in the SERPs, depending on the keyword search.
I probably could not word it any better then the original post, so here it is:
I had a page with a spelling mistake on it, and the word was only used once, so there was no right version on the page, only the wrong version.
Searching for the right spelling, the page did not appear to be indexed, at all; which led me to wonder why... until I spotted the spelling mistake. The page ranked as a normal result for this incorrect spelling.
I corrected the error and the page ranked for the correct spelling within a few days. It was a normal result. The cache is updated daily and when searching using the correct spelling the snippet shows the correct spelling too.
If you search for the incorrect spelling, then the page is still shown in the SERPs, and the snippet shows the content with the WRONG spelling too. That is, the snippet does not reflect either the real page content, nor does it reflect the cached page either! The "wrong spelling" result does have a title and snippet and it has been a supplemental result for at least a month now.
The page is a normal result if you search for anything else to do with that page. It is only a supplemental result for a search using the spelling mistake.
When looking at the cache, when clicked from the spelling mistake search, the cache shows the very latest page content; but it says about the keywords "these terms only appear in pages linking to this page". Well, that is not true (unless you want to bend the truth a little). The spelling mistake only appeared on that page in the past, and is not there now. The spelling mistake is not on any page that links to the page in question (unless you count the Google search as being a page that links to it!).
The only way to get to that place is via: http://www.google.com/search?q=keywordspeltwrong