Saw that happen @ Road America one year. Turn 5 had a tire wall chicane in the runoff to slow you down so you wouldn't go back on track at turn 13. Guy got to the brake markers and found he had no brakes and no way to scrub off enough speed to make the chicane. He landed and slid within feet of the ambulance. IIRC, he wasn't hurt more than bruises. Turned out someone on his crew didn't safety wire the pins in his calipers and the pads bounced out.