Oh boy, you picked the wrong web designer - we've seen it many times. Fortunately, not all is lost if you act quickly enough. Many times this is done by a designer with little SEO experience doing things such as; changing URLs but not 301 redirecting, removing content, leaving a noindex meta tag, disallow on the robots.txt, or not setting the SEO title properly. A good SEO agency can rescue parts of this by identifying and fixing what was missed.