If your airline confirms to you that your luggage is at YUL and you wish to take possession of it yourself, you can always come to the airport. However, be sure to ask your airline for their hours of operation.
When you arrive, go near the doors 28 at the arrivals level. You will see phones in front of these doors. Follow the instructions on the black phones and an agent will answer you and tell you how to pick up your luggage.