96 Lesabre ABS lght

After a brake job by a shop. My wife is drivng along 2 days later and the rear wheel locks up. Ironicly, it happened almost in front of the shop that did the job. They take it in and discovered that the small spring on the top was missing. They fix it and now the ABS light will not go out. The brakes feel better than they ever have. I call the guy and he says he couldn't get it to go out that sometimes they do that. Obviously I am done with this guy at this point.( lets not argue this) Now what I am wondering is. Is the light the result of the wheel locking up or something the shop did ? It wasn't on after the initial brake job. I bled the brakes to see if that would help and it didn't. Everything looks good under the hubs. The calipers and rotors look fresh The reservoir is up to level. I disconnected the battery. I remember hearing about a little known reset button. Does anyone know of this? Also, are the ABS faults stored on the OBD ? I am thinking it is a hard fault that was to be reset by a real ABS trained tech. The book I have says almost nothing about the ABS other than not to mess with it. I do not have a scanner. Any ideas on this would be appreciated .