In early August, I booked a flight to London via Montreal on AC.
As I boarded, I was told I needed to check one of my carry-ons. I refused when I saw that they had no luggage receipts, but when I was told I wouldn't be allowed to board, I handed it over.
The flight ended up being cancelled for mechanical reasons.
I was rebooked for the next day via Toronto and gave my luggage receipt and a description of the carry-on - I got the checked bag but no carry-on; after waiting around for 2 hours, I was told it had been put on a flight to Montreal!
I've jumped through all the hoops, there is an official file on my bag - but I basically have given up hope.
Among all the lessons of what to do differently next time, number one is always have ID tags on all bags, even the ones you never expect to be separated from. (Probably a no-brainer for frequent travelers…)
Number two is, never fly Air Canada again; avoid any airline that is trying to save money by not giving bag receipts for plane-side bag checking.