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.
Facebook doesn't notify users when their posts are screenshot. This is the case whether it's a photo, a status update, or a link post. It's all about privacy and the user experience. If such a notification were enabled, it might discourage people from interacting with posts in a normal way. So, no, someone can't tell if you screenshot their FB post.
Facebook doesn't give any indication to the user who made the post that someone has taken a screenshot of it. You can screenshot posts for your own records or to share with others privately without the original poster knowing. This is in contrast to some platforms that do notify for screenshotting, but Facebook values the freedom to save and share information in this way.
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.