User clicks on your site. You redirect to a fake search page and then redirect to your page after setting a cookie. Now back button sends them to the fake search results.
Independent of anything else, allowing the back button to take you back to a page that redirected you previously is bad UI. It is almost never the desired behavior.
User clicks on your site. You redirect to a fake search page and then redirect to your page after setting a cookie. Now back button sends them to the fake search results.