You can call the embassy and ask for an emergency Travel Document (it's like a passport but typically only used to get you back into Canada).
At the same time, you need to file for a citizenship certificate replacement. The only significant issue here is the regular replacement will take 16 months (
click here to see the timeline).
The way around this is by putting a request of urgency on your application. If done correctly, it will take 2-6 weeks for the replacement. Here is some info about this topic,
click here (scroll down to "urgent processing."
The last thing you should do is call IRCC and make sure your urgent request will work (it depends on your request and the documents you submit).
Click here for IRCC info
P.S. I hope FedEx finds your certificate, in my experience, it could take a few weeks, but in most cases, they find the package.