Help needed, high pitched grinding noise from front end of my A4

Driving home from work and all of a sudden i heard a high pitched grinding noise coming from the front, turned the stereo down and opened the windows and I could hear it, sounded like its coming from wheel area rather than the engine. It lasted all of about 2 miles and then went away and hasn't come back.
I had new shocks and springs around 3 months ago and nothing was noticed when they were fitting.

It sounded like metal on metal grinding, i had a quick check of the discs and pads when i got home and they still look good with good life left in them, so what could it be. Car still drives fine.

What could this be, your help would be very much appreciated

Thats what i'm hoping, it was as I turned into a rather dusty lane as a shortcut around the M1, lots of pot holes on the edge of the road, the noise happened for approx 2 miles, then as I got back onto smooth A road and picked up speed the noise went and hasn't returned since. Braking seems fine, engine seems fine

thanks,
I took the car out to the local tesco to do some shopping (of course) and everything seems fine. And again this morning on the way to work. Was very worrying at the time, especailly as i'm looking at selling her soon. Thanks for the replies guys.