Hi
check the passport you used to enter Canada with. Next to the immigration stamp or label, the immigration officer should have stapled the IMM5292 to the passport... It looks like an insignificant piece of paper (carbon copy) and I myself almost threw it out since I didn't think it was so important to keep after receiving the actual PR card.
Don't ever throw it out. Not only do you need it for Citizenship, you will need it for Old Age Security.