SJRK-289 was deployed to the server, all of the old stories ceased to be served because they're missing the "published" flag.
The work to solve this issue should be two steps:
1. Temporarily change the storiesById database view to allow both published stories AND those where the published flag is undefined, and make a similar change to the handleGetStory request handler
2. Update all of the old stories to have "published: true" in their data, then revert the step above to allow only published stories to be served publicly
3. Add tests to anticipate such issues as best as possible
As jobara mentions in the comments, a better long-term solution would be version tracking for the records themselves and some migration tools.