I changed out my old brake pads today with some stoptech ones and I noticed that when I did a few 80-0 stops that I could not get the ABS to engage for the life of me. Also now that I think of it my ABS wasn't engaging during the winter either the brakes would just lock up.
Check the fuse. And how long have you had the car? Was it tuned before you got it? The light could have been turned off and a blown fuse put in there. I wouldn't blame them if they did that... My 02 would be slowing down fine in slippery going and then all of a sudden the ABS would kick on and it felt like I goosed the throttle because the car would rocket forward... Not fun, nor safe. Throwing myself into a skid would be safer. I could stop my father's Saturn with all seasons on it faster than my wrx with snows when the abs was on vs none on the saturn... Anyway.. Check the fuse. The light might be just shut off.