I never knew it was at the bottom and I use this site all the time. Thanks for pointing that out. However, it does raise some questions about the UI in this case. Can't we put the search box up in the header where people expect it to be?
I only tend to use search now and again, since it's not always used I prefer it not take up initial screen space. Also I think the majority of HN users are able to figure out a way of searching this site relatively easy, I see it as a non-issue.
I think the happy medium would be to add a link to search in the top bar but not the actual search bar.
Indeed I also didn't know about this. In general I don't think it is easy to find information about how to use hacker news, everything is hidden in weird places.
I tend to run Google searches like these - site:news.ycombinator.com 'AI'