If you are unable to find a column that is present on your different instance in a slush bucket ,then it may have been added as a result of package/plugin activation.

Here is how to check this
Example -- Columns Resolved_at and Resolved_by are no where to be found on instance A but then we see that they exist on instance B.

1. Go to the dictionary record (sys_dictionary) of the column resolved_at(Resolved) or Resolved_by(Resolved by) on table Incident on the instance where it is present in list view.
2. Go to personalize list and add package (***NOTE*** the package field is an inherited field from the 'Application File' (sys_metadata)  table which means this field exists on every descendant table within the sys_metadata hierarchy).
3. Copy the value in the package field as this corresponds to the plugin package which the field comes from.
4. Go to System Definition > Plugins
5. Search for the name of the plugin and then confirm if the plugin is active.
6. In the example provided, the status of the Incident Resolution Fields plugin should be active to see the fields on Incident.

 (The information presented does not only apply to columns on a table but to any serviceNOW artifact on an instance. If a user/admin discovers that a particular artifact is present in one instance but not in another, the steps provided can be utilized to see if the issue is derived from a plugin that has not yet been activated which loads the artifact which the admin/user is looking for).