What message does pipeTo send on a timeout or other failure?

In Akka, rather than using onComplete on a future response created with ?, I am trying to use pipeTo because that is supposedly the preferred pattern. However, I don't seem to be receiving any Throwables or Failures when the future times out. What should I expect to receive in my actor if a timeout occurs when using pipeTo? What about when a different exception is thrown? Example code:

class Simple(otherActor : ActorRef) extends Actor{
  def receive = {
     case "some_msg" => {
       val implicit timeout = Timeout(1 seconds)
       val response = otherActor ? "hello" 
       response pipeTo self
     }

     // case ??? // How do I handle timeouts?
  }
}

If no message is automatically sent when a timeout occurs, how am I supposed to handle timeouts with pipeTo?