I have a data extract activity which is pulling tracking extracts for unsubs. The ListID return by unsub tracking extract is different from the ListID return by the _ListSubscriber data view. In documentation, listId is the id of the list which is used for sending email. This is strange that the same subscriber has two different listID from tracking data extract for unsub and _listSubscriber data view.
From the information you provided in your comments, it sounds like the Subscriber has unsubscribed from all list.
This can occur when they click the "Unsubscribe from List" link at the head of your email in email clients like iOS Mail and Gmail; example here. These links send a technical message to SFMC, resulting in the record becoming unsubscribed from all relevant lists.
You can double check this by viewing the Subscriber Properties in ALL SUBSCRIBERS, and checking if the unsubscribe date for all Lists/Publication Lists is the same.
Also remember that your email customers can open emails from many months ago and click Unsubscribe - we often find unsubscribe requests come in from emails that we sent many months ago.
You also have access to the Publication Subscriber and Unsubscribe Data Views if you need to check the Subscriber's activities across your other lists. These additional views will give you more complete view of what has happened to your subscriber.
It may not be the case here, but there is a largely unknown feature where if more than one Data Extension is targeted in a single send and a publication list is used, the system will assign each Data Extension their own associated 'List ID'. Even though each data extension may be referencing the exact same publication list, one Data Extension will get the actual publication list ID, and the others are assigned a temporary ID, which Salesforce Support called a 'virtual' publication list id.
As a result you may be seeing the virtual ID in your unsubscribe table, while the _ListSubscribers table maintains the actual ID of the publication list.