Have you tried replacing get_thumbnail with:
<a href="https://wordpress.stackexchange.com/questions/28431/<?php the_permalink(); ?>" title="<?php the_title();?>"><?php the_post_thumbnail(); ?></a>
Have you tried replacing get_thumbnail with:
<a href="https://wordpress.stackexchange.com/questions/28431/<?php the_permalink(); ?>" title="<?php the_title();?>"><?php the_post_thumbnail(); ?></a>