It turns out that this is a "ghost xref" caused by an internal "drive remapping" acheived by using a batch file to reamap internal drives as corresponding network drives for when we work remotely. It greatly reduces time since it does not have to communicate with the server onsite. It was necessary to duplicate the offending XREF onto the other drive. Now the unreferenced xref no longer shows up.
I discovered this by observing that this issue did not present itself when at the worksite, without the drives remapped. I then ran the batchfile to remap the drives and the issue reappeared. This was never a "legitimate" issue since the drive remapping incited it!
The batch file coding:
@Anonymous_off
echo REM ECHO THIS COMMAND TRANFORM A SINGLE FOLDER IN NETWORK DRIVE LETTER C:\SANDUSKY IN DRIVE E: REM
echo REM ECHO THIS COMMAND TRANFORM A SINGLE FOLDER IN NETWORK DRIVE LETTER C:\SANDUSKY\ACADE\BLOCK EM DRIVE I: TO LOAD ALLLIBRARY BLOCKS REM
net use E: /d /y
subst /d E:
net use I: /d /y
subst /d I:
subst E: C:\SANDUSKY
REM \\san1eng1\electrical REM
subst I: C:\SANDUSKY
REM \\san1eng1\library REM
PAUSE
Lee M.