I've changed my top-ranking page to a simpler URL on the same domain with a 301 / permanent redirect, and changed sitemap and internal links accordingly.
A couple of days later Google crawled the site, indexed the new URL and dropped the old one.
My fears became true: despite recognizing the new canonical URL for the old indexed page, the page has vanished from the search results.
Would it help to revert the changes (that would mean that Google has kept some history of the old page rank)?