I have owned a page that has ranked in the top 3 for over 7 years and gets traffic from hundreds of different keyword combinations related to the subject. It's an evergreen informational page on a subject that will remain popular as it is something we do in every day life.
A few days ago it disappeared from Google for a dozen of the best keywords, but not all of them, and traffic was reduced by 40%. The untouched keywords however... it remained #1 to #3.
Then I noticed that another site which has also had a similar guide up for 4 years had moved to the #1 spot after having been behind me most of those 4 years. Next to the results for this site there is a little down arrow with the options "cache" and "similar".
When I click on "similar" then I see my page as #1 again, of all the similar pages.