Hi
Have you customized search.php file? By default demo, if there’s nothing in search result, it will show a message like http://demo.themevan.com/oldcar/?s=css
If you want to show the message when there’s no search result, you should add the following php code in the search.php
<?php if (!have_posts()):?>
Your message here......
<?php endif;?>
This is only a general idea, because the customization issue is not include in the support service.
Thanks!!