Get VIM Object by reference using vCloud plug-in

Hello, any suggestions on how to retrieve a VIM object by reference from a vCloud host?  I'm attempting to get the resource pool(s) backing provider vDCs.  Here's what I'm trying that's producing a null result:

for each (var vcdInstance in VclHostManager.getHostList()) {

     vcdInstance.login();

     for each (var pvdc in vcdInstance.toAdminObject().toAdminExtensionObject().getVMWProviderVdcs()) {

          for each (var rp in pvdc.getResourcePools()) {

               var rpVimObj = vcdInstance.getEntityByReference(VclFinderType.VIM_RESOURCE_POOL, rp.resourcePoolVimObjectRef);

               // rpVimObj is null

          }

     }

}

I've also tried a couple variations of finder types like VclVimObjectTypeEnum.RESOURCE_POOL as well as using rp.resourcePoolRef as parameters to getEntityByReference.  The vCloud host/plug-in version is 1.5, using vCO 5.1.