Say a site removed their forum. You can go to the site and view other things like articles. Even the link to forum is gone. So you google something and it comes up with one of the threads, even displays the text. You click on it and it takes you to 404 page not found. Where did google find the info and was still able to send you to the correct website even though the forum is gone. When I say gone. The website(magazine) still exist however the owner even wrote a message the forum has been removed on its homepage as a short article listed with usual news and what’s happening.

Maybe the Wayback Machine can help.

There are a couple of different scenarios.

1. Because the information is still on the website, and Google crawled the site, so they know it exists.  But they removed the forum functionality, so you (public) simply cannot access it anymore.

2. They removed the information (Which would be dumb) and Google simply hasn't recrawled the entire site yet. Hopefully they didn't do it this way.

There's a lot more to this (like why you don't want 404's on your site)..

But that's it in a nutshell.

Thanks Hasbeen. Learned something with a little bit of searching

Cache

Google has a bit of a grace period on 404s, where something that used to exist will still turn up in search results after it's been removed by the owner. But, eventually, those results will disappear too, and it will vanish from existence...

The Wayback Machine is your best bet for old content, especially if you know what URL you're looking for, but if it's something that's only been recently created it may not turn up there for a time.

Oh, and Google or Bing's cache of a page (as linked to from a search result) MAY return the content you're looking for, but I've noticed that's been more miss than hit lately (no cache links, cache link can't be found, etc.)