how do I change an objects tag when the game closes

Question

I'm making an inventory script, and I change the tags of prefabs to check if my inventory already has them stored, but when I exit the game the tags stay as stored. this is a problem because then it doesnt add or instantiate the prefab. here's the code if it helps

  public void AddObjInv(GameObject InvObj, int amount)
    {
        
        if (InvObj.tag != "stored")
        {
           GameObject InvObj2 = Instantiate(InvObj, new Vector3(transform.position.x + 1.0f, transform.position.y, 0f), Quaternion.identity, this.transform);
            if (transform.localScale.x == 1)
            {
                InvObj2.transform.localScale = new Vector3(-1, 1, 1);
            }
            InvObj2.name = InvObj.name;
            InvObj2.SetActive(false);
            StoredObj.Add(InvObj2);
            ObjAmount.Add(amount);
            InvObj.tag = "stored";
        }
        else
        {
            ObjAmount[StoredObj.IndexOf(InvObj)] += amount;
        }

    }

I tried OnApplicationQuit, but it wouldn't change when I stopped testing.