A vaginectomy is just to close the opening/remove most of the vaginal canal once a hysterectomy has been done (or during the hysterectomy if done with a meta procedure). While sometimes part of the vaginal tissue is used for a urethral extension during a meta, it's not as if a full phallic graft could be made from it, or it isn't currently anyways. For one, the vaginal canal is not skin, it's a mucous membrane, It doesn't look or feel like skin, it's very textured. Also very pink. XD I guess stranger things have happened, but I can't imagine they'd be mutilating people's forearms and thighs if such a graft were possible.