Several months ago I shut down a page, on the rock-solid grounds that it was thin, boring, and nobody ever visited. Its content got shifted onto a newly created page, along with lots of other miscellaneous stuff, leading to the suitable redirect
/directory/oldpage.html >> directory/newpage.html#oldpage
Over the months, I remained baffled at the number of search-engine redirects from this page. (No humans, because I said nobody ever visited, and I wasn't kidding.) Honestly, they seemed to be requesting it more often than they did before I retired it.
Finally as a last resort I fired up Text Wrangler and did a comprehensive search for “oldpage.html” in my local site files.
Yup, found one.
Would anyone care to guess where I found it?
On the /directory/ index page. Yes indeed. I’d entirely forgotten to remove the old link ... and to add a link to the new page. I’d duly updated the navigation banner, but forgot all about the index page.
Incidentally: I then wandered over to GSC to see if they'd told me about this issue and I ignored it. Turns out there is a listing of URLs that aren't indexed because they redirect--but it doesn't distinguish between “all URLs we have ever heard of” and “URLs that are continuously reinforced because you yourself link to them, you incompetent webmaster you”.