purchased phone that was later reported stolen/lost, AT&T blacklisted but offers no help?

Iphone was purchased locally and reported stolen after about two weeks..... I contacted at&t, however they respond only with, since you did not buy it from us we wont help you..... why will they not contact the original owner..... ? Even to return the phone? Is there anything I can do with the imei to track this information? Maybe it was a mistake? How can I find out any information?