Correct, time and votes aren't sufficient to explain story rank. This is in the FAQ:
Q: Why is A ranked below B even though A has more points and is newer?
A: You can't derive rank from votes and time alone. See "How are stories ranked?" above.
From "How are stories ranked?": Other factors affecting rank include user flags, anti-abuse software, software which demotes overheated discussions, account or site weighting, and moderator action.
Right, thanks, that part I had figured out. The detailed weightings don't concern me, but could you let us know if this involved moderator action (vs. automatic), and whether the ranking was hard-capped?
Q: Why is A ranked below B even though A has more points and is newer?
A: You can't derive rank from votes and time alone. See "How are stories ranked?" above.
From "How are stories ranked?": Other factors affecting rank include user flags, anti-abuse software, software which demotes overheated discussions, account or site weighting, and moderator action.
https://news.ycombinator.com/newsfaq.html.