I don't know how long Google keeps their cache, I can't find that information, but I know that I've upon occassion found sites that were gone (by some time) via their cache instead. Supposedly I guess that the cache would disappear when the site is no longer indexed, ie due to disappearance, but that is a tough one - a site might be down, when do they consider it gone? OTOH, any site owner may request that Google does not cache their site, which is somthing like an opt-out solution then I guess.
By your definition, I guess theirs is a grey area then.
You have moved into a dark place.
It is pitch black. You are likely to be eaten by a grue.