Index: src/wp-admin/js/theme.js
===================================================================
--- src/wp-admin/js/theme.js	(revision 28886)
+++ src/wp-admin/js/theme.js	(working copy)
@@ -190,6 +190,12 @@
 			return match.test( haystack );
 		});
 
+		if ( results.length === 0 ) {
+			this.trigger( 'query:empty' );
+		} else {
+			$( 'body' ).removeClass( 'no-results' );
+		}
+
 		this.reset( results );
 	},
 
Index: src/wp-admin/themes.php
===================================================================
--- src/wp-admin/themes.php	(revision 28886)
+++ src/wp-admin/themes.php	(working copy)
@@ -233,6 +233,8 @@
 </div>
 <div class="theme-overlay"></div>
 
+<p class="no-themes"><?php _e( 'No themes found. Try a different search.' ); ?></p>
+
 <?php
 // List broken themes, if any.
 if ( ! is_multisite() && current_user_can('edit_themes') && $broken_themes = wp_get_themes( array( 'errors' => true ) ) ) {