If you look closely at the walls of the wheel itself, you should see a lead weight, in length it is about an inch check your front wheels to see if there is one missing, If the car has alloy wheels these weight are on the inner rim of the wheel, you said it may have been the road!! make sure you have this right, The imbalance as said would have effected your steering when you noticed the Vibrate, but you can drive out of this by increasing your speed, but that does not solve the wheel imbalance.