In the official akka 2.0.4 docs it says:
An actor restart replaces only the actual actor object; the contents of the mailbox is unaffected by the restart,
You already get the failing message in preRestart (see: message: Option[Any]) so no need to stash it away yourself. And yes, it is perfectly fine to re-send it to yourself, but beware of infinite restarts in combination with this since you'll most likely end up with a message that will never be discarded.