Suppliers and their contacts are also created in HZ_PARTIES. The supplier is an organization, where the contact is a person. They get a relationship in HZ_RELATIONSHIPS (usually type CONTACT_OF).
You can query the suppliers in hz_parties with their relationships as follows. They can be related to site or to top level.
Note that HZ_RELATIONSHIPS usually contains two records. One for the PERSON-ORGANIZATION relationship (type CONTACT_OF) and one for the ORGANIZATION-PERSON relationship (CONTACT usually). You can check on subject_type and object_type to make sure you fetch the right relationship.
, hr.status relation_status
, org_party.status org_status
, cont_party.status contact_status
, hoc.status contact_status
from hz_org_contacts hoc
where hr.relationship_id = hoc.party_relationship_id
and hr.subject_id = cont_party.party_id
and hr.subject_table_name = 'HZ_PARTIES'
and hr.subject_type = 'PERSON'
and hr.object_type = 'ORGANIZATION'
and hr.relationship_code = 'CONTACT_OF'
and hr.object_id = org_party.party_id
and hr.object_table_name = 'HZ_PARTIES'
and asup.party_id = org_party.party_id
and hoc.party_site_id IS NULL
and org_party.status = 'A'
and cont_party.status = 'A'
and hoc.status = 'A'