If you booked your (paid) ticket through CX.com, you can still retreive your booking online even without a MP account, provided you created a login name and password on CX.com when you bought your ticket (I think that's required if you don't have an MP account). It's not easy to retreive it; I know, I tried yesterday. But it can be done.

Go to CX.com and roll over the "Manage Your Trip" bar on the left, then click on the "Retreive Your Booking" button. That will take you to a screen that allows you to punch in either an MP number and PIN or your login ID and password. Enter your login ID, and your booking will appear. It's pretty limited functionality after that point, though. I couldn't see how to check seat assignments or anything.