PHP Codeigniter 4 redirect route not found after insert

Question

I have a controller that calls my model to insert a new record, returned the id of the new record, and then does a redirect to display the new record. But I get an error: "The route for '/r/xx' cannot be found". My Routes.php has a route:

 $routes->get("/r/(:num)", "Home::showRec/$1");

The controller code:

   $rid = $mymodel->mSaveNew($data);  ##return correct new id
   if ($rid === false) {
       $this->session->setFlashdata('errors', "?system error adding new record");
   } else {
       $this->session->setFlashdata('messages', "*** Added new record #$rid");
   }
   return redirect("/r/$rid");  ### this fails ###

What is wrong with my route?

The same redirect() route called in another controller method for updating an existing record works fine.