Your plugin works great except for one minor issue. We use https for wp-admin and had to modify your plugin so it would work correctly.
Here's the small change you need to make in file-unattach.php line #71:
define('FUNATTACH_URL', WP_PLUGIN_URL . "/" . FUNATTACH_FOLDER . "/");
define('FUNATTACH_URL', plugins_url("/" . FUNATTACH_FOLDER . "/") );
That function auto-detects if https is being used or not.
Would be great if you could make this change in your next update. Thanks.