From the documentation:
DeathWatch for Akka Remote does not (yet) get triggered by connection failures – which means that if the parent node or the network goes down, nobody will get notified. This feature may be added in a future release of Akka Remoting. Akka Cluster, however, has such functionality.
http://doc.akka.io/docs/akka/2.1.0/general/supervision.html#What_Lifecycle_Monitoring_Means