In https://example.org/guide#packing, the part after the hash sign can direct the browser to a place inside the resource. It is worth separating that fragment from the path before troubleshooting a link.
Change the fragment, keep the document
The MDN fragment reference explains that the fragment is not sent to the server as part of the HTTP request. The browser processes it after retrieving the resource. A typical HTML example uses an element with an identifier matching the fragment.
Create a local practice page with two headings, giving them different IDs. Link to each with a hash reference and watch the page move. Then try an ID that does not exist. The document may still load successfully even though the intended destination cannot be found.
Do not mistake browser-side processing for privacy
Scripts running in a page can read its location and fragment. A fragment is therefore not a suitable place to hide sensitive information from the page itself. The fact that it is omitted from the initial HTTP request is a narrower technical property.
When reporting a broken section link, include the full URL and the heading you expected to reach. Also note whether the page has changed since the link was created. A server returning the document successfully and a visitor reaching the correct section are two checks; only the second confirms that the fragment still does useful work.
AI-generated editorial illustration; not a documentary photograph.