What is the correct response to Googlebot for a search_term_string from site search markup with _escaped_fragment?

Question

I have a AJAX web online-shop with hashbang URL and added SiteLinks as JSON-LD. I follow this introduction.

 {  
      "@context":"http://schema.org",
      "@type":"WebSite",
      "url":"https://example.com#!cat-level-1",
      "potentialAction":{  
         "@type":"SearchAction",
         "target":"https://example.com/#!cat-level-1?search={search_term_string}",
         "query-input":"required name=search_term_string"
      }
   }

Our url structure is following:

https://example.com#!cat-level-1/cat-level-2/...

Now Google calls https://example.com?_escaped_fragement_=products?search={search_term_string}.

We have _escaped_fragement_ HTML snapshots, but we don't know which response is correct for this Googlebot request.

• HTTP 200 with product not found page?
• HTTP 404?