PO Fax output change log

Hi All,

I have scenario where PO was created in the year 2014 and has Fax output triggered but not  processed. Now suddenly that fax output is processed and fax is sent to vendor. I checked in NAST but there is no information on who processed FAX output. NAST table store only the username of creator of output. I also checked processing log and Further data for output message but it also does not have that information. Also there is no information of PO change log too. Does anyone know how we can get information on who processed the PO output.

regards

Chetan