I see your example.
Passivation occur because of a limitation of resources on the container.
If you write a client to acces your bean, the instance of the statefull bean
will be pooled. It will not be passvivated since there only one client.
Try to specific code in ejbPassivate() to see what it's happening
(Put a System.out.println in ejbPassivate).
The eror message don't give any information about passivation.
It said
The EJB does not exist
I think your EJB is not deployed. Try to redeploy it and see...
Hope it help.