Unassigned Reference Exception on assigned variable?

Within a script, on the Start() function, I assign a GameObject variable bulletSpawnSpot to a child of the object. This child is where i want bullets to spawn from, it does nothing more. I do not have the bulletSpawnSpot variable assigned prior to launching the game, it is only assigned after it runs it's Start() function. upon running a debug after assigning bulletSpawnSpot, it prints that indeed, bulletSpawnSpot is assigned to GameObject BulletSpawnPos (name of the child). But when i call the FireShot() function, I use bulletSpawnSpot.transform.position and bulletSpawnSpot.transform.rotation to spawn the bullet at the game object, but i get the following error when i try to fire http://imgur.com/iKdUJMu Here's the code for assignment

 void Start () 
 {
     player = GameObject.FindWithTag("Player");
     cam = Camera.main;
     foreach(Transform child in transform)
     {
         if(child.gameObject.tag == "PlayerBulletSpawn")
             bulletSpawnSpot = child.gameObject;
     }
     Debug.Log(bulletSpawnSpot.ToString());
 }

Again, that debug prints that bulletSpawnSpot = BulletSpawnPos, which is what i want. but when i call the FireShot function...

 public void FireShot(int bulletType)
 {
     if(bulletType == 1)
         PhotonNetwork.Instantiate("Orange_Bullet", bulletSpawnSpot.transform.position, bulletSpawnSpot.transform.rotation, 0);
     Debug.Log("FireShot");
 }

...it gives me the error posted above. Also, I'm calling the FireShot() function from the player's handler script

 if(Input.GetButtonDown("Fire1"))
     {
         bulletScript.FireShot(currentWeapon);
     }

Not sure if that would affect it. Any ideas?

P.S. I'm rather new to Unity (started just over a week ago) so if this is some noob mistake, that's why c: