Trying to get post thumbnail or attachment

Hi there,

I am trying to create a custom front page for a blog where I display a post thumbnail (featured image) or an attachment image, if the featured image is not set.

I get the featured image to display but there is no attachment image showing up with this code, even though there is an image in the post content.

// options come from custom field
	$args = array(
		'cat'=>$blog_exclude,
		'posts_per_page'=>$posts_per_page,
		'paged'=>$paged
	);
	query_posts($args);
	// $posts_remaining = $wp_query->found_posts-$offset;
	while (have_posts()) : the_post(); 

	// the current post has a thumbnail (featured image)
	if (has_post_thumbnail()) {
		$attr = array(
			'class'	=> "post-thumbnail",
		);
		echo '<a href="' , the_permalink() , '" class="post-thumb-link">';
		the_post_thumbnail('full', $attr);
		echo '</a>';
		$has_thumb = ' with-img';

	// the current post has NO thumbnail
	} else {

		// check for attachments
		$args = array(
			'post_type' => 'attachment',
			'numberposts' => -1,
			'post_parent' => $post->ID,
		);
		$attachments = get_posts( $args );
		// display the first image if there is one
		if ( $attachments ) {
			foreach ( $attachments as $attachment ) {
				echo '<a href="' , the_permalink() , '" class="post-thumb-link">';
				echo wp_get_attachment_image( $attachment->ID, 'medium' );
				echo '</a>';
			  }

			$has_thumb = ' with-img';
		 }
		}

Any ideas?