This issue is now resolved for us. It appears the "DEV" in question was buried in a Sub-Site of a Sub-Site. Once the form was deleted from the list there, and "Delete Local Cache" was done on the Nintex Mobile App the form disappeared.
So, I preferred last weeks "Ghost Forms" issue over my newest Nintex problem... "Ghost Actions". Uhm, yah, now today's issue is with Nintex Workflow Cloud not showing actions in Designer and Workflows Failing SharePoint connections. Every day is a brand new adventure using this product. #TechSupport