We might looking at the same seats, I checked on Wed and found 4 seats on VIE-YYZ everyday at the end of August, then all gone, yesterday.
On the other hand, 4 seats for YYZ-VIE opened up towards the end of June, so I just reversed my direction and grabbed those. On top of that, I also got 4 seats on AC 34 YVR-YYZ, I believe that is the continuation flight from SYD. ^