I assume you sent your original application package to CPC-Mississauga. This is where the sponsor is approved. So the sponsor approval ALWAYS comes from CPC-M, before the package is mailed to the outland visa office (in your case was Seoul). So the fact that your app is in Manila now, means you are 100% guaranteed to already have sponsor approval, though for some reason they didn't send you the email or letter. If you didn't get sponsor approval, the app would have stopped in Mississauga.
You can always call CIC and tell them you didn't get a letter, and they'll send you a new one.