It takes a lot to warp a rim. If he couldn't get it to zero balance,and you don't see a visable dent or flat spot...I would say it's the tires(assuming that you didn't have the vibration before). Cheap tires are know for these problems,and the same goes for tires that were stored for a long time,or sat in one spot leaning against a wall. I've had rims that have had major gouging with a flat spot(dent),and they were still able to be balanced.....so I really think that it points more towards the tires.