Again, sorry to hear about that. But Clay bar will not work - it is meant for like a soft polish only.
You need to try a light-duty automotive paint thinner (I used one called R-2) which should immediatly remove roadpaint and not your car's paint. As long as you don't push too hard or work it too long (to go down through clearcoat), you should be fine. If you are worried about using it, you can always wax the area after / and then use you clay bar!
good luck