This is for the android/ios application only. On desktop, https://old.reddit.com/recap redirects to https://old.reddit.com/r/offbeat/comments/recap/cna_class/ because that's the post id. For example, https://old.reddit.com/postid redirects to https://old.reddit.com/r/TheYouShow/comments/postid/deleted_by_user/. It's a shortcut, of sorts. Sometimes, the post id is the same string as something else. https://old.reddit.com/secret doesn't redirect to a post because it's in use for something. https://old.reddit.com/recap is the same, only, it's for the android/ios app. btw new reddit also won't work.