Hibernate joined-subclass salva mas não funciona load() nem get()

Programação Java
#1

Fiz um mapeamento de subclasses usando joined-subclass ele funciona normalmente pra salvar mas o session.get() retorna null

org.springframework.orm.ObjectRetrievalFailureException: Object of class [br.com.xxx.CampoData] with identifier [1]: not found
        at br.com.xxx.CampoDataDAOHibernate.getCampoData(CampoDataDAOHibernate.java:38)
        at br.com.xxx.CampoDataManagerImpl.getCampoData(CampoDataManagerImpl.java:34)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:585)
        at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:310)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:155)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:122)
        at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:57)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:144)
        at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:174)
        at $Proxy5.getCampoData(Unknown Source)
        at 
......

hbm resumido


<hibernate-mapping
	package="xxxxxxxxxxx">
	<class name="Campo" table="CAMPO">

		<id name="id" column="ID_CAMPO" type="long" unsaved-value="0">
			<generator class="hilo">
				<param name="max_lo">100</param>
			</generator>
		</id>

		<property name="nome" type="string" column="NOME" />

		<many-to-one name="tab" class="Tab" column="ID_TAB"
			not-null="true" />

		<joined-subclass name="CampoTexto" table="CAMPO_TEXTO">
			<key column="ID_CAMPO" />
			<property name="tamanhoMaximo" type="short"
				column="TAMANHO_MAXIMO" />
			<property name="valor" type="string" column="VALOR" />
			<property name="valorDefault" type="string"
				column="VALOR_DEFAULT" />
		</joined-subclass>

	</class>
</hibernate-mapping>
#2

Session.get() não retorna somente se já estiver no cache?

#3

não… ele deveria funcionar mesmo(na minha opnião)…

api spring
Return the persistent instance of the given entity class with the given identifier, or null if not found.

api hibernate
Return the persistent instance of the given entity class with the given identifier, or null if there is no such persistent instance. (If the instance, or a proxy for the instance, is already associated with the session, return that instance or proxy.)

#4