No matter where the game itself is installed, it will try to write configs to your user folder, which Windows by default will have on C:
If it's not there it should definitely be creating a new one. You may want to paste %USERPROFILE%\Documents\Mount and Blade II Bannerlord\Configs into an explorer window address bar in order to go there directly in case you were checking a different user's directory.
If it's certainly not present, you may want to check OneDrive to see if you got signed out or are it's having syncing issues, as problems with OneDrive can mess with user folder permissions, but normally that kind of issue would cause the game to simply crash on launch.