If it was only one tank of gas and you didn't push the car to its limits I honestly do not think that it did any significant or even small damage. A few tankfulls, however, could potentially mess your engine up. I am not a pro, but theoretically it shouldn't have done any damage in such short term. And if it did, you'd certainly hear it since the damage would be with cylinder heads and other in the combustion chamber- the very process that makes it all work.