There is a cancellation, and then there is an alteration/change. If the guest cancelled, there is no need for the host involvement. You would simply be advised that the booking was cancelled,a nd you could see this in your Reservations (you can see every single reservation by going through the list).
If the guest altered the booking to change her checkout date to an earlier date, you would receive a notification of this, and you'd have to agree to it. It's really easy for these things to get lost in the mail, but the record of it would be active in her reservation for the duration of the stay. Not sure if the record of the alteration request stays in your dashboard post-stay, but check in your notifications. In theory, if the guest requested a change, and you did not approve it, your payout should have been for hte entire booked amount through January 5th. You should be able to see in your transaction history whether you were paid in full, and then you can contact Airbnb about it (how to contact airbnb is at the top of the Community posts). But it's now two weeks later, how come it's taken so long to follow up? Not being snarky, I just wonder if there is a technical issue that prevented you from seeing payouts, etc. You should have had your payout December 27th, and then you should have seen any change to the payout by at least January 2.....