Because the Hunter 38 has a sugar scoop transom, it may be around the corner on the side of the hull on the starboard side.
If there has been a repair in the area it may be possible to see the number with a pencil rubbing. Place a piece of paper over the expected location and rub it with the side of the pencil, much like a gravestone rubbing.
The secondary location is often a closely guarded secret, it will be placed somewhere that is not easily accessible and may require cutting into the hull liner. The purpose of this hidden location is to identify stolen or severely damaged boats.
If the boat has a questionable history of ownership, a prior owner may have removed the number. Hope it is not this.