I would do the same thing here as if one had been in Toronto or any other place in Canada where there would not have been a national boundary crossed.

Amass receipts and backup for expenditures in the other city, whether in Canada or elsewhere. Rather than relying on just the FFP printout, include the e-ticket receipt showing that you were scheduled to fly and, if by some chance you have the BP or a copy stored, include that as well. The more paper the better.