This works for any story you can legally view (public or your own) on m.facebook.com.
Step-by-step:
Warning: This finds the temporary CDN link, which expires within minutes. Https M.facebook.com Story.php Story-fbid Download
Since you are specifically looking at m.facebook.com (the mobile site), you are likely on a phone.
If you do not want to use third-party websites (to avoid ads or privacy concerns), you can try finding the video source directly using the mobile link: This works for any story you can legally
The link you provided is the direct internal address for a Facebook Story on the mobile web version.
The Challenge: Unlike standard videos on Facebook (which have a "Download" option in some contexts or easily accessible direct file links), Stories are encrypted or streamed in a way that prevents a simple "Right-click > Save As." This has created a market for third-party "Facebook Story Downloaders." Warning: This finds the temporary CDN link, which
Traveling or living in an area with poor internet? Downloading a story allows you to watch it later without data.