Contact the DCFS office in the county where you were in foster care. Ask to speak to their Post-Adoption Support Unit. Ask for all information that you can have from your file. You will not be given names or other identifying information about your birth family.
Well, first of all, there is no mention that the OP was adopted, but she was in foster care. So what gives you the impression that they would help her.
Second, what gives you the belief that they will give her ANY information? The person she spoke with is correct. The records belong to them, and they are, by statute, not obligated to share their information with anyone without a court order.