As many websites are built by clever people and/or based on somewhat ready-made frameworks, when you DON'T see the RSS/Atom icons appear -> take a look at the source of the website and search (ctrl-f) for the word "rss" or "atom" or "xml" -> you might end up finding a surviving RSS link in there.
This is a big part of why I think that making feeds better discoverable could help a lot. Often the feeds are still there, but the browsers are not showing it to the site visitors.
So that you know, that's autodiscovey, not some weird remnant. That's so you can just put the URL for the page in your feed reader and it can find the feed(s) for you. Browsers with RSS support detected it, too.
As many websites are built by clever people and/or based on somewhat ready-made frameworks, when you DON'T see the RSS/Atom icons appear -> take a look at the source of the website and search (ctrl-f) for the word "rss" or "atom" or "xml" -> you might end up finding a surviving RSS link in there.