In slightly more detail now: what
@steaky and I are both saying is that when you arrive at the land border crossing, you will tell them you have lost your PR card but you're a PR and reside in [wherever]. Then you show them
whatever you can to help support the case you are making that you are a PR.
"Better" in this respect is a copy of PR card, COPR, your UCI#, etc, and in descending order other docs/correspondence that show you are a PR, docs that show you live in Canada, etc.
The goal of this is to make it easier for them to identify you as a PR and match it to their computer files. Part of this is goodwill - eg showing an active driver's license or health card will give them a fair degree of comfort you do, indeed, reside in Canada. (Oh, sidenote, if you have a police report that it's lost, may also help that case, although probably not required).
Because once they've established ('satisfied') that the individual in front of them is a PR, they must let that individual in. They do not seem to play games with this, although the interaction can be more or less pleasant and quick depending on how quickly they come to this conclusion (and the 'human factor').
Steaky is right that your foreign passport will probably be enough - they match at least by name and DOB. The other evidence will make it more likely they do it quickly and spend less time on confirming you-are-you.