Might be some thread merging, dang sometimes does it, or might be a newish automatic feature I haven't heard about.
Oddly, if you search the story name it says it was actually posted 3 days ago, but directs tot his thread:
https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu...
You can email them and ask, email's in the faq. They do respond.