Hold on...you've changed the theme on your WP site(which is live) but the site itself is not showing in search results? I'm a bit confused because of the way that sentence is worded. Do you mean to say that just the website itself is not showing up in results or is the site showing up on results, but visitors don't get the new theme when it loads?
I highly doubt it's a problem with the web crawler if it's got nothing to do with the results and more of a technical problem on your end. Web crawlers constantly crawl to grab information and grab new sites to add to results.
I don't use WP but is there any error messages or that which we may be able to work with?