An ArcGIS Portal item from an orphaned resource cannot be removed.

Workaround

1. Use the Remote Desktop Protocol (RDP) method to access the portal machine and navigate to the items directory for the subject item. E.g. C:\arcgisportal\content\items\1a44401d384241398dd984a14d73ffae\resources
2. Create a file of the same name and location that the orphaned resource is looking for.
3. Remove said orphaned resource. The file is gone.

Steps to Reproduce