The folder that I was deleting here did contain the .xmp file shown in the screen shot. Can or better yet should IMatch be set up to recognize this xmp file?
IMatch automatically recognizes XMP sidecar files of course.
The most likely reason for this warning are some orphan XMP files left by some other software.
XMP files without a matching image indexed by your database that is.
Follow IMatch's advice and check the folder.
If you sure it and all files contained within it can be deleted, do so.
Thanks, I will do that.