Have a go on a deserted parking lot. Make sure you have ample space. Accelerate to 30mph, then stomp on the brake -- as hard as you can, don't be afraid. If you hear a buzzing sound, and feel pulsation under your foot, ABS works. If you don't, and wheels lock, pump the pedal to brake properly and safely as if in a car without ABS. And assume your ABS is malfunctioning.

Your might have been lucky and your ABS bulb might have just burnt out. That doesn't solve the real problem, though (if any).

Cheers, Kuba