From a snapshot (on a story slide) you can navigate to the sheet and visualization it originated from. By doing this you get access to the live data of the snapshot where you can make new selections to take your story in new directions.
Do the following:
In storytelling view, navigate to a story slide with a snapshot.
Right-click the snapshot.
The snapshot's shortcut menu is opened.
Select Go to source.
You are directed to the sheet where the snapshot originated from. And the visualization which the snapshot was taken of, is initially highlighted.