Bingo. First of all thank you so much for the reply and the suggestion. Files, in fact, are just there. Hidden but there (on Mac with cmd+shift+[dot] missing files are displayed).

Anyway to unhide them permanently, the way is a bit more long to follow and requires a command by the terminal:

chflags nohidden

leaving a space after "nohidden" and dragging the files into the terminal window. That will fill out the path to each of the files. Then hit return.
(If they were hidden with the hidden flag, they will no longer be hidden).

And it works.

Thank you so much Steven, you made my day !!!