I don't know if I'm underestimating HN's reach but I doubt we did that, probably traffic from a much bigger aggregator/forum
Hacker news doesn't generate much traffic, despite what people are saying.
The host here has a limit of 160000 files served each day. That is extremely low. If the site has an icon, css, a js file and a few images it's 10 files each visit. That's will limit it to 16k visits/day. If there are more files loaded it might just handle a few thousand visits, and they have received more than that from HN now.
You are underestimating HN's reach, this happens all the time. As someone who has been on the front page of HN it's a pretty big rush in traffic!