Really what you need is the PNR history, specifically the location and agent sine of who cancelled the return. If it is the agency, it will show an agency "pseudo city." If it was AA it will have the location and agent who cancelled those segment. It will also tell you if AA auto cancelled them for some reason.
You can send a request to AA's corporate security as they have control of previously flown PNRs, but I am not sure what kind of response you will get back.