pacman -Qo use local database - pkgs installed (not pacman -FY .files)
we have always local filenames database
as pacman -Qs is only local
local:
ls -l /var/lib/pacman/local/linux*/files
pacman -Qo file_in_package_installed
pacman -Ql package_name_installed
pacman -F use pacman database (all pkgs, installed or not)
Sync filenames database is an option with pacman (but we have always with pamac)
as pacman -Ss is for all (Sync database)
ls -l /var/lib/pacman/sync/*.files
pacman -F filename
pacman -Fx "in path or filename"
pamac search -f file (as pacman -Fx)