How do I include thumbnail in Latest Post shortcode?

I have successfully created a shortcode in my theme for displaying the latest post. Unfortunately, I can’t get the post’s Featured Image (AKA thumbnail) to display. Any thoughts or advice would be greatly appreciated.

// Short Code for Latest Post
add_theme_support( 'post-thumbnails' );
function my_recent_posts_shortcode($atts){

 $q = new WP_Query(
   array( 'orderby' => 'date', 'posts_per_page' => '1')
 );

$list = '<div class="recent-posts">';

	while($q->have_posts()) : $q->the_post();
		$list .= '<a href="' . get_permalink() . '">' . get_the_post_thumbnail('thumbnail') . ' ' . get_the_title() . '</a>';

	endwhile;

	wp_reset_query();

return $list . '</div>';
}

add_shortcode('recent-posts', 'my_recent_posts_shortcode');