Try that in the thumbnail file
PHP Code:
<div class="thumbnail-wrap">
<?php
if ( has_post_thumbnail() ) {
echo '<img src="';
wptouch_the_post_thumbnail();
echo '" class="attachment-post-thumbnail" alt="post-thumbnail" />';
} else {
$portfolio_full = get_post_meta($post->ID, 'portfolio_full_img', true);
$post_image = get_post_meta($post->ID, 'post_image', true);
$disable_post_image = get_post_meta($post->ID, 'disable_post_image', true);
echo '<img src="' . $portfolio_full . '" class="attachment-post-thumbnail default-thumbnail" alt="post-thumbnail" />';
}
?>
</div>