I flew YYT-YOW via YYZ yesterday (March 3rd) with my return flights originally scheduled for tomorrow (March 5th). I requested upgrades over the phone on March 2nd and received a confirmation of upgrade for my first flight, AC443 YOW-YYZ departing at 0800 on March 5th and I was added to the waitlist for YYZ-YYT. I was just glancing at my AC app earlier today prior to checking in and noticed that it now only showed me as flying from YYZ-YYT as if I had booked a multi-city itinerary; the Ottawa flight segment had disappeared without any notice. I called reservations to try and figure out what was going on and was simply told that 443 was canceled (it is not, I can still see it as on time in the app). I informed the agent of this and she very quickly said "no sir, I can see that it is canceled." I was not interested in having a lengthy argument with the agent so after a bit of back and forth I accepted the new routing that I was told was the only option, which now has me leaving YOW at 0605 connecting in YUL to 674 to YYT, but with a 6-hour layover.

Does anyone have any idea what happened here? It is like the segment just disappeared, yet the flight is still scheduled!