I honestly don't see how any structural damage could occur from a RUB unless you and I have different definitions of a rub. chances are what your feeling may be the paint. I know the paint on my bike is incredibly thick. If you are really worried about it you can get a new aluminum road bike frame from nashbar for $80 as they have a 20% off one item sale going on right now. So I wouldn't fret too much, frames can be had for fairly cheap.

Also i will add that there is another thread discussing someone that had an aluminum frame where the dropouts and seat stays were bent significantly. Someone with knowldge of metals said generally Aluminum has one bend init. meaning if you do something that messes it up and bends something it will still be structurally sound, you just probably won't be able to bend it back without it breaking. this is different than steel which is very bendable.

I would have zero fear of something rubbing on my bike, I'd have a lot more fear if something of significant weight fell on it. Remember, bikes are crashed and often times it's just a few scratches and cosmetic damage, i'm almost certain thats what you have unless you show us a pic that looks otherwise.