I don't understand, should be in the standard spot, on a plaque under the windshield on the bottom, (driver's side?). You see it from outside the vehicle. There isn't really any good reason why that plaque would not be there, unless the vehicle was stolen and someone removed it for that reason prior to resale.
It should also be on the vehicle registration/title, which your father should have if he owns it, unless of course it was stolen and a false VIN was used. Granted having it on the registration may not be enough to satisfy a tech inspector as they need to document that this specific vehicle has that VIN #.
It should also be on the sticker on the end of the driver's door or the adjacent door latch panel, but sometimes those wear away.