SO deleted the vG VNF stack and then send a DELETE request to SDNC. SDNC reported an error: 

Returned FAILED for vnf-topology-operation [d482d39a-3bed-4326-87c1-b46137561089] VnfTopologyOperationOutput [_ackFinalIndicator=Y, _responseCode=400, _responseMessage=No preload data found to match vnf-name, _svcRequestId=be43e101-e1f7-4f45-80bb-9f7dee140e5f-1510262498173, augmentation=[]]

The vnf name used by SDNC to do the query was:  zRegionOne39_base_vcpe_vgw_0

2017-11-09 21:21:48,500 | DEBUG | p443827396-41826 | SwitchNodeExecutor | 295 - org.onap.ccsdk.sli.core.sli-provider - 0.1.2 | test expression ($vnf-topology-operation-input.vnf-request-information.vnf-name) evaluates to zRegionOne39_base_vcpe_vgw_0
2017-11-09 21:21:48,500 | INFO | p443827396-41826 | SvcLogicExprListener | 294 - org.onap.ccsdk.sli.core.sli-common - 0.1.2 | Outcome (zRegionOne39_base_vcpe_vgw_0) not found, keys are { ("") (Other)}