This seems to do it…
add_action( 'init', 'tr_hide_custom_type_search', 99999 );
function tr_hide_custom_type_search() {
global $wp_post_types;
if ( post_type_exists( 'gd_place' ) ) {
// exclude from search results
$wp_post_types['gd_place']->exclude_from_search = true;
}
}