Add a comment for [27073] as someone will inevitably complain it is tricked by % in a string. see #25604.

git-svn-id: https://develop.svn.wordpress.org/trunk@27074 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/wp-db.php

@@ -1053,6 +1053,7 @@ class wpdb {
 		if ( is_null( $query ) )
 			return;
 
+		// This is not meant to be foolproof -- but it will catch obviously incorrect usage.
 		if ( strpos( $query, '%' ) === false ) {
 			_doing_it_wrong( 'wpdb::prepare', sprintf( __( 'The query argument of %s must have a placeholder.' ), 'wpdb::prepare()' ), '3.9' );
 		}