As of now, Facebook does not notify the person who posted a story if you take a screenshot of it. So, in general, no one can see that you've screenshot their FB story.
Facebook doesn't currently have a feature that allows you to see if someone has screenshot your story. This is mainly for privacy reasons. People share things on their stories with the expectation that others can view it briefly, but screenshotting is something that can't be easily monitored by the platform in terms of notifying the story creator.
As of now, Facebook doesn't provide a built - in mechanism for users to be notified if someone screenshots their story. This is different from some other social media platforms. For example, Snapchat has a feature where it notifies the sender if a screenshot is taken. But on Facebook, you can screenshot a story without the owner being aware of it. This is part of Facebook's privacy and user experience design. It allows users to freely capture and save content they find interesting on stories without the worry of the original poster being notified.
Well, as of now, Facebook doesn't have a feature that allows users to see who has screenshot their stories. So the answer is no. It's different from some other social media platforms where such notifications are enabled. This is mainly to protect user privacy to some extent. Because if people knew their stories were being screenshot all the time, they might be less likely to post certain things. So for now, you can screenshot a Facebook story without the owner knowing.