My fixed gear bike is equipped with a front rim brake. It was this front brake that didn't work -- noticed later that the quick release was in the "open" position, and my brakes pads are worn waaaay down so the brakes put almost no stopping pressure on the front tire.
Because I use a front brake, I'm not nearly as adept at stopping on a steep downhill with the rear-wheel only that I might otherwise be. After a moment of panic, however, I managed a skip stop with about a half dozen skips before I finally slowed enough to stop.
nice save! i've had similar issues arise (like a pedal-strap breaking when i had no brakes!), damn it can be scary.
i've also had the pleasure of doing a long skid (going downhill, towards a redlight of course), and having the tire pop! just wore straight through and then put a hole in the tube! damn these fixies wear out tires (and tubes) fast...