Is there a way in which a Trigger is not fired?

We have this situation:

We have a table and there are rows that are been deleted. We need to know who and/or when these row are deleted.

We create this trigger:

ALTER TRIGGER [dbo].[AUDITdel_nit] ON [dbo].[Client]
 FOR DELETE
 AS
 Insert into AUDIT select 'Delete', getdate(), 'Row Deleted', SYSTEM_USER, host_name(),
 (select 'ID Client: ' + convert(varchar(12),Id)  from deleted), 'Client' ,APP_NAME()

We made somte test: deleting rows vis stored procedures and the deleted rows appears in our AUDIT table.

But suddenly today we found a row deleted that dont appears in the AUDIT table...

Any idea how it can be done?