Dead Post Redirect

Hi –
We have a number of older posts we’ve set to draft status. Following your support I created a new 404.php file in our child theme. I put in this code:

<?php
header(“HTTP/1.1 301 Moved Permanently”);
header(“Location: “.get_bloginfo(‘url’));
exit();
?>

But when you go to links from removed/draft mode posts, you still get this page:
Nothing Found
Sorry, the post you are looking for is not available. Maybe you want to perform a search?

Why aren’t these pages redirecting to the frontpage?