I'll take a look at this. You should have a orm.xml inside a META-INF directory inside your classpath that contains the definition of the query, like this:
https://github.com/krisv/jbpm/blob/master/jbpm-gwt/jbpm-gwt-server-war/src/main/resources/META-INF/orm.xml
There seems to be a similar issue on JIRA already, I'll update that with the necessary information.
https://issues.jboss.org/browse/JBPM-3057
Kris