Getting a Post’s Featured Image URL By Post ID
<?php $feat_image = wp_get_attachment_url( get_post_thumbnail_id($post->ID) ); ?> <img src="<?php echo $feat_image; ?>" width="80" height="100" />
If Featured Image else your default image:
check below code:
<?php $feat_image = wp_get_attachment_url( get_post_thumbnail_id($post->ID) ); ?> <?php if($feat_image) {?> <img src="<?php echo $feat_image; ?>" width="80" height="100" /> <?php } else {?> <img src="default.jpg" width="80" height="100" /> <?php } ?>