unable to wp_enqueue_script(‘suggest’);

As stated on WP Devel, you should always use the appropriate hooks. Else no child theme could deregister the script later.

// In your functions.php file
function add_suggest_script()
{
    wp_enqueue_script( 'suggest', get_bloginfo('wpurl').'/wp-includes/js/jquery/suggest.js', array(), '', true );
}
add_action( 'wp_enqueue_scripts', 'add_suggest_script' );

This will load the script from the includes folder and stick in your footer (where a script ideally should be).

You could also use includes_url() in the function above. This will also check for SSL connections.

Note: You’ll have to have wp_head(); present. Inside there the mentioned hook gets fired.