Below is how I solved my issue. The SOURCE was not seen in the INSERT as a result set as I wanted. It was nothing for the INSERT. I just rewrote the queries in such a way that the result set be seen in the INSERT. Thanks a lot user2919277.
INSERT INTO Discarded.JournalDet
(JournalDet_ID, Amount, Sensoa, DetoaId, ID_Agency, JournalId, Appli_Source, ReasonDiscarded, DateDiscarded)
SELECT SOURCE1.JnlDetoaId, Amount,Sensoa,DetoaId,ID_Agency,JournalId, 'GameApps', 'Member not yet inserted', GETDATE()
FROM Journaldet AS SOURCE1
inner join Agency AS SOURCE2 ON SOURCE2.Agency_ID = SOURCE1.AgenceId
WHERE ((SELECT COUNT(Journal.Journal_ID) FROM dbo.Journal WHERE dbo.Journal.Journal_ID = SOURCE1.JournalId)=0)