Index: post-thumbnail-template.php
===================================================================
--- post-thumbnail-template.php	(revision 18627)
+++ post-thumbnail-template.php	(working copy)
@@ -83,11 +83,10 @@
  * @since 2.9.0
  *
  * @param int $post_id Optional. Post ID.
- * @param string $size Optional. Image size.  Defaults to 'thumbnail'.
+ * @param string $size Optional. Image size.  Defaults to 'post-thumbnail'.
  * @param string|array $attr Optional. Query string or array of attributes.
  */
 function get_the_post_thumbnail( $post_id = null, $size = 'post-thumbnail', $attr = '' ) {
-	$post_id = ( null === $post_id ) ? get_the_ID() : $post_id;
 	$post_thumbnail_id = get_post_thumbnail_id( $post_id );
 	$size = apply_filters( 'post_thumbnail_size', $size );
 	if ( $post_thumbnail_id ) {
@@ -102,4 +101,27 @@
 	return apply_filters( 'post_thumbnail_html', $html, $post_id, $post_thumbnail_id, $size, $attr );
 }
 
+/**
+ * Retrieve Post Thumbnail URL
+ *
+ * @param int $post_id Optional. Post ID.
+ * @param string $size Optional. Image size.  Defaults to 'post-thumbnail'.
+ * @return string|bool Image src, or false if the post does not have a thumbnail.
+ */
+function get_the_post_thumbnail_src( $post_id = null, $size = 'post-thumbnail' ) {
+	$post_thumbnail_id = get_post_thumbnail_id( $post_id );
+
+	if ( ! $post_thumbnail_id ) {
+		return false;
+
+	do_action( 'begin_fetch_post_thumbnail_html', $post_id, $post_thumbnail_id, $size ); // for "Just In Time" filtering of all of wp_get_attachment_image()'s filters
+	if ( in_the_loop() )
+		update_post_thumbnail_cache();
+	$size = apply_filters( 'post_thumbnail_size', $size );
+	list( $src ) = wp_get_attachment_image_src( $post_thumbnail_id, $size, false );
+	do_action( 'end_fetch_post_thumbnail_html', $post_id, $post_thumbnail_id, $size );
+
+	return $src;
+}
+
 ?>