Not during the normal course of changing a tire, but who knows what they really did.... If you are going to return to the tire place to tell them you think that they did it you will have a slim chance of proving it; but I guess it is worth a try.
Don't be cheap in attempting to cut the rotor as BMW doesn't sanction it and that one looks like you would have to remove a lot of metal to get it flat. Buy a new one. The other side looks reasonably new so even though I don't reccommend it you might get away with just changing the one side. Usually they are changed in pairs per axle.