WP_Query get_the_post_thumbnail not working

Hello,
I am trying to make custom widget which shows the most recent post in the Project category. It should give me the post title, the thumbnail if there is any or a default image, the excerpt and link to read more of the post.
This is my code for the widget:

$args = array( 'posts_per_page' => 1,
                       'post_status' => 'publish',
                       'cat' => 'Projects',
                       'orderby' => 'date',
                       'order' => 'DESC',
                       'post__not_in' =>get_option('sticky_posts'));
        $query = new WP_Query( $args );
        if ( $query->have_posts() ) {
	        while ( $query->have_posts() ) {
		        $query->the_post();

                $author = get_the_author();
                $excerpt = get_the_excerpt();

                echo '                  <div><h5>'. get_the_title() .'</h5>
                    <a href="'. get_permalink(). '">
                    <div class="img-border">' . check_for_thumbnail() . '</div>
                    </a>
                    <p>
                    ' . string_limit_words($excerpt,20) . '
                    <br>
                    <a class="more" href="' . get_permalink() . '">view more</a>
                    </p></div>';
            }
        }
        wp_reset_postdata();

and here is my check_for_thumbnail() function code:

function check_for_thumbnail() {
        if ( has_post_thumbnail() ) {
                  get_the_post_thumbnail();
        } else {
                  echo '<img src="' . get_template_directory_uri() . '/images/noimage.jpg" alt="no-thumbnail-to-show"/>';
        }
}

The problem is that it does not outputs neither the thumbnail nor the default image. Also if change get_the_post_thumbnail() to the_post_thumbnail() it outputs the thumbnail of the post but no in the <div class=”img-border”></div> but on the top of all the content.
Can somebody please help me about this?