When did you add that custom field exactly? What data is being exported from your Pipeliner system? What date was that user created?
These are all the types of questions that the Audit Log can answer for you. Users with access to the Audit Log get to see a log of all the changes made in the Admin module over time and can filter by Date, User and Category ⤵
All the main Admin areas are tracked including adding and changing users, updating pipelines and adding custom fields.
You can export the Audit Log to Excel or CSV and manage who can see the Audit Log in User Roles.