Media files disappear after upgrade to Big Sur 11.2.3

Does anyone know of a way to retrieve XDCAM media files,

which were deleted after upgrading to BIG SUR.  The file

icons on my MAC PRO TOWR 2019, are greyed out and

Apple tech could not retrieve the files.  Appreciate if anyone

would let me know if they had this experience.

Gloria Messer  [deleted by mod]