If you can still see the volunteer’s name in a search, the likelihood is that the profile has been archived. This would still allow you to view the profile, but the volunteer would be restricted from seeing anything related to your organization (Custom Fields, Qualifications, General Interests, Availability, Activities, Contacts).
If the account you are able to see is not Archived, the volunteer may have more than one Better Impact account. Please verify the volunteer is logging in with the exact same username you can see on their profile.