There are several ways to add someone to a campaign – through a bulk request, a manual add, a trigger, and more. You may want to check how someone was triggered into a campaign for several reasons. To do so, follow these simple steps to view the internal source – how the particular contact was added to the campaign.
If you click "Trigger", you'll be redirected to the specific trigger that put the contact in the campaign. If you click “Contact detail page" you'll be taken to their contact record.