The radiator support VIN number location had no "set" specific place.
Most are found either on the top or back side, from the midline of the car to way over by the battery.
I have seen some that were hidden below the radiator coolant sticker as well, so feel for bumps under it.
If you do not find a number at all, it may have been hit & repaired before. They used to sell the complete radiator support as an assembly for collision repair.