CIC说的很清楚啊:
If your PR Card is lost or stolen while you are outside Canada, you should report the loss or theft to the nearest Canadian visa office. To return to Canada, you’ll need to apply for a permanent resident travel document (PRTD). It is only valid for one entry into Canada. Once you are back in Canada, you can apply for a replacement PR card. You must fill out section G (solemn declaration) when completing the application and pay the $50 processing fee.