IN OUT PObject parameter not updated

Question

Server and client: 11.1.0.6 linux 32 bit, connecting with via a ConnectionPool.
I'm passing a PObject parameter to a procedure as an IN OUT parameter. The object is passed in OK, but it appears that none of the object attribute modifications that the procedure is performing are making it back to the object representation in the C++ application. The equivalent procedure call in PL/SQL works as expected, passing an instance of the type to the procedure results in modifications to the type attributes after the call, so I've eliminated the procedure as the source of the problem.
The procedure follows. I've attempted it without NOCOPY without any difference.
PROCEDURE create_user (user_in    in out nocopy USER_T ) IS
BEGIN
    insert into user (
      user_id
     ,username
     ,password
     ,first_name
     ,last_name
     ,created_by
    ) values (
      user_id_seq.nextval
     ,user_in.username
     ,dbms_crypto.hash(UTL_I18N.STRING_TO_RAW(user_in.password, 'AL32UTF8'), 3)
     ,user_in.first_name
     ,user_in.last_name
     ,user_in.preferred_tzformat
     ,sys_context('OWNER_CONTEXT', 'user_id')
    ) returning user_id into user_in.user_id;
END;The C++ call, UserT is the OTT representation of the USER_T Oracle type:
UserT* user = new UserT();
user->setUsername("user1");
user->setPassword("pass");
user->setFirstName("me");
user->setLastName("me");
sth->setSQL("BEGIN create_user(user_in=>:p1); END;");
sth->setObject(1, (PObject*) user);
sth->executeUpdate();
cout << "New user id: " << user->getUserId() << endl;user->getUserId() results in an error to the effect that the number is NULL, meaning the procedure update has not made it to the client.
This works:
declare
  u user_t := user_t();
begin
  u.username := 'user2';
  u.first_name := 'me';
  u.last_name := 'me';
  u.password := 'blah';
  create_user(u);
  dbms_output.put_line('Userid: ' || u.user_id);
end;

Answer 1

Update:
I've added a getObject() call after the executeUpdate(), and now debugging indicates that the PObject readSQL is being called (writeSQL is being called for the executeUpdate).
And, within the readSQL function I am in fact able to print out the correct user_id value directly in readSQL after the assignment.
But, my class getter function, which simply reads the previously assigned user_id member, still giving the NULL error, strange.