Kia Carnival SX Dead Battery @ -21c

I love my Kia Carnival, I keep telling myself this, it's cool, its techie, and I tell people all the time it's awesome, until it isn't.

In Ontario this morning we are experiencing a cold snap, -21c / -5.8f with a windchill of -40 so it's cold. I have a very important business meeting 1 hour away and I'm prepped and ready to go. At 7am ish I get a notification that my doors are no longer locked on my Carnival (Keys are not on me, they are on my dresser) and I get the notification out of the blue on my phone. I know that I locked the door last night and used the app to confirm it later in the evening so it was a little weird. To confirm, I used the app to relock the doors and it tells me that I have not started the engine in some time or I'm in a bad reception area (I ran it yesterday, and never had reception issues while in my driveway). I go to start it, same error. I bundle up, and go out to have a look and my Carnival is there dead. Car was purchased in May, battery is less then a year old, dead. Car won't open, won't unlock and won't start.

For those of you who haven't tried it yet, the Kia fob separates into a fob and a mechanical key, there is a little inset button just below all the other buttons on the side of the fob and it will let you take the mechanical key from the fob. That mechanical key goes into a tiny slot on the underside of the drivers door and lets you remove the right side of the door handle to get access to the mechanical lock.

Once you're in the car, well you're in a car with a dead battery, you can open the hood, that's about it.

We've called CAA, we tried our booster, it didn't give it enough juice to start the car, even when left on to charge the battery.

Some suggestions:
Before this happens to you, have a look at the process to take when your battery no longer works. Separate the keys, try the mechanical locking / unlocking. Open the hood, look at the battery, its an odd mess under there of connections and get familiar before it happens at -21c.
When you go to replace the piece of the handle that comes off, make sure it's warm (it might be brittle if cold) and you have to pull the handle out to get it back in without scratching the other piece of the handle.

The car is booked for a maintenance next week, I'm going to request a new battery, but I doubt I'll get one.

Edit: Aftermath
CAA came and had a rough time boosting it, it took about 20 minutes of fiddling before we could get it to go, but we finally got it up and running.

I contacted Kia and their response: Maybe you didn't shut it down properly and left it on accessory all night, or maybe there was a door ajar all night that drained the battery.

Issue #1: Shouldn't the first issue resolve itself? If you let the engine idle it will auto shut off after 30 minutes, and in accessories in 10 minutes?
Issue #2: Wouldn't I get a notification on the app, I'll test when its warmer.