mike wrx

Ok so had the rear brakes changed on the wrx the other day an on driving off the abs light popped on, so took it back today and on the drivers side we noticed that behind the disc a jaggered ring was dented in part way round and on pocking it alil with hammer it snapped, so just really needing to know what exactly its called and where id get 1 from? Il post a pic when get in of the culprit but lad that did brakes said it was abs sensor ring or sumthing