Our search is powered by a Google custom site search.
If the post you are looking for isn't showing up, there's a few possibilities.
1) It's a very new post and Google's custom search hasn't indexed it yet. Unfortunately, this index isn't as fast as the main Google index.
2) Your site doesn't show up very well in English-language Google search results. This is a known issue for non-U.S. sites and something we will remedy.
3) Your site is having Google search issues. If your site is in English and you are not getting good results, you may want to see if your site is having issues with search.
Somethings to look into: Do you have a sitemap? Is your robots.txt file telling Googlebot to stay away? Are there indexing issues (sign-up for Google Webmaster tools)? Are you SEO optimized? (YOAST is a very easy to use WordPress plugin that helps you get the basics right.)