A family of Microsoft word processing software products for creating web, email, and print documents.
That is a good and clever suggestion. I found a version in one other location...
"C:\Users\danss\AppData\Roaming\Microsoft\Templates\LiveContent\16\Managed\Word Document Bibliography Styles\TM02851226[[fn=turabian]].xsl"
... which is similar to one of yours. However, the file name is altered and copying the vancover.XSL file there did not work.
So since the paper is due tomorrow I used a workaround and reformatted the citations manually.
This was probably a one-time need, hence the urgency, but I am not going to pursue the matter further.
Thanks for your efforts.