It is stored in the database: eCallByCallStat.EventData
From the Nortel Contact Center Manager, Historical Reporting and Data Dictionary:
EventData, Description: The information related to or generated by this event. The data can be a PIN entered by the caller in response to the collect digits command; an ANI, CLID, site ID, or activity code; or reasons for the event.
Type: varchar
Length: 40
Database view:
Call-by-call statistics use the eCallByCallStatYYYYMMDD view.