For whatever reason if a person has disappeared off the system or you can't find them in the member list, use the search box in top right of navigation. You can search by first name, last name or email.
When I go to the Members List page, why do I not see who I am looking for?
In the case where you know someone was in the system and has been a member before but you don't immediately see them in the Member List page, it could be because their plan is either Completed, Cancelled, on Alert status or Paused.
To find these members look appropriate status in the right rail of Members List page.
For a complete searchable list. Use the Download Members button at the bottom of this right column to download a CSV file of everyone in the system. You can get a similar download of all your Leads from the Lead list page.
Also, if you have connected your Mailchimp or Autopilot account, your members should be over there too, which you may want to segment for more precise targeting.