Thanks for taking the time to review HNSearch.
Your example search is sorted by date so it makes sense that the words "billion" and "almost" don't necessarily appear in the title. Here are the search results sorted by relevance:
http://www.hnsearch.com/search#request/submissions&q=bil...
If you'd like to filter on stories with those words in the title, you can use the "title:" operator:
http://www.hnsearch.com/search#request/submissions&q=tit...
Did you try sending us an email with your feature requests? Usually we respond very quickly to emails about feature requests.