class SomeActor extends FSM[State, Data] {
  when(Idle) {
      case Event(GetChild, _) =>
          val child = context.actorOf(Props[ChildActor])
          sender() ! child
          stay.using(/*save state here*/)

val getChildFuture = someRegion ! Message(id, GetChild)
val child: ActorRef = Await.result(getChildFuture, timeout.duration).asInstanceOf[ActorRef]
// do something with the actor ref here