Join the club man. I think we've all done it once or twice. Sometimes we forget it's as low as it is.

After about a year I ended up replacing my front bumper (not due to this but due to other stupid things I did). On my new bumper i caught the top of a parking bump and put some little small scratches on it. I ended up filling them with touch up paint and you can't tell unless you crawl under the front.

It would seem like the liner could work but i have not heard of anybody try it...