Have you tried the search at the bottom of this site? (Just in case you missed it)
Anyway, I think this might be the submission you're looking for:
https://news.ycombinator.com/item?id=25357315
At least it's the one that came to my mind when I read your description. Being able to vividly remember posts from 86 days ago makes me feel a bit anxious about how much time I spend on HN and how much of my brain is allocated for storing what I read here.