As you will find in other posts on this forum, it is absolutely possible to leave without your card and return, however, you need to be from a visa-exempt country or have the previously mentioned PR travel document.
Here is my story from earlier this holiday season. I got my PR confirmation in November, and called CIC to set up my landing interview. I work 5 minutes away from a CIC office, so thought I would just get it out of the way instead of doing it the next time I enter Canada. During the call, I asked whether I would have any trouble traveling while my card was being processed, and they said no.
I go and do my landing process and at the end I was informed that I can't travel unless I have my PR card or apply for a PR travel document while outside of Canada. I was leaving on holiday in two weeks, so a rush order on the card wouldn't work. Fairly frustrated with the whole thing, I call CIC and ask why they would tell me that it was OK to travel. The answer I got, and I'm not joking, was "I think my colleague meant that it's no problem for you to leave, however, coming back is an issue". To me, traveling means the process of leaving and coming back, but enough about that... I then call CBSA to check whether they would allow me to enter Canada with my passport and COPR, which they said wouldn't be a problem. Technically you are allowed to enter Canada by car with your COPR and passport.
Luckily, I'm from a visa-exempt country and the new travel visa rules are not yet in effect, so I decided to go on my holiday and bank on the airline letting me board the flight from Europe as a visitor. I had zero issues checking in, boarding and entering Canada. Just gave them my passport and boarding pass and that was it, no questions asked. As other people have mentioned in other posts, don't mention that you are a PR as they might start asking for your card. At the border, I explained my situation (told them I was a PR, showed my COPR, etc.) and there were no issues.
Hope this helps.