Did you "share" your field extraction? If not, no one but the user who created it will be able to see it. You can update the permission on the field extraction by going to Manager and editing the Permission for this Extraction.
You may need to use the field picker. Within the left window pane, you should see a pick fields link. Select the link and choose your new field. It should then persist for this particular source.
Note - you will need to share the extraction if you want to use it collaboratively.