The Marriott reservation # does show up on the II confirmation page. I only found this out a couple months ago.
Look at your II Confirmation Certificate (the pdf file). On the right hand side (light yellow). The last item in the top section shows: Reservation number. This is the Marriott reservation #. Go to Marriott.com and log into your MR account. Then put in the reservation #. It should pull up your reservation for the II exchange. You can then add your Marriott Rewards # to the reservation. Once you've done this, it should show up in your "Upcoming Reservations" section. I've done it for our next two II exchanges into MVCI properties.
Don't use the II Confirmation Number which appears on the left hand side under your name and address.
It takes a few days for Marriott to reassign the confirmation number from the name of the depositor to the exchanger. In the past, I have called immediately and the reservation is still in the original name. Usually, 3-4 days is all you need to wait for it to be in your name.
ONE OTHER IMPORTANT THING I HAVE FOUND. The Marriott Confirmation Number MAY change......I had my membership rewards number assigned to a completed exchange. (exchange for additional Surf Club Week) It showed up in "My Reservations" on Marriott.com etc. One day, it was gone from marriott.com. Naturally, being the calm, cool, collected guy I am.....I PANICKED. I called Marriott and (although it took a while) determined that II changed the week they were giving to me. Not the unit size or calendar dates of the week, simply the inventory. As a result, the original Marriott confirmation number was not valid. I called II, got the new onw and everything was fine. I spoke with II about this. As far as they are concerned, the Marriott confirm. number is irrelevent. You have a confirmation number from them and an active exchange. (I don't believe this happens often, but it can.)