Has this been done before? I'm in a situation where I need a column hidden from content managers and only visible to the super admin.
This is definitely not core functionality for Matrix.
You would need to either write a custom extension that would hide the column from non Super Admins or find another add-on to help.
One possible solution is to use the Securit:ee add-on's encryption fieldtype, which allows you to configure which member groups can view the unencrypted data in a field. If you used this fieldtype for your column, then it should only allow the groups you specify to see the data. Of course this is contingent upon your column being a text field and not some other fieldtype.