'No posts' missing from search.php

I’ve created a search.php file to display the search results of some custom posts using the loop below:

<?php if ( have_posts() ) : ?>
<?php $posts = query_posts($query_string . '&orderby=title&order=asc'); ?>

<?php while ( have_posts() ) : the_post(); ?>
<?php endwhile; ?>

I want to show some text if no posts are found, but if I add an ‘else statement anywhere’ I get the white screen of death. Any ideas?