If a ConfigurationItem object hasn't been updated for 30 days, it will be marked as stale and would be deleted,
Confirm whether the ConfigurationItem objects are updated frequently, and how long before an object would be deleted, these can help to confirm whether the objects have not been updated for a very long time and was deleted due to its stale state.
If so it's expected.
The user can also set "60" or more days for stale objects to be deleted for HostBaseObject.
In Object Cleanup dashboard click on HostBaseObject | Auto-delete | choose "delete when stale for x day".
Here the user can set 60 (or other integer).
Then click OK to save and confirm if the ConfigurationItem objects remain for additional days.