This only works for public profiles. If you’re friends with the person or their profile is private, you’ll be blocked by the login screen.
If you hover your mouse over a Story thumbnail on Facebook Desktop, or long-press (but don't release) on the mobile app, you often get a 1-2 second preview. This preview usually does not register as a view because you haven't technically clicked into the Story. view facebook stories anonymously
Since the story was pre-cached (pre-loaded), you can see it while offline. Force close the app This only works for public profiles