We have probably stayed on AP rates 10 or 12 times in the past 10 years and have never yet had anyone even ask us to see the pass (yes, we always have them). Once they asked if we were AP holders and I said yes and that was it. I am sure if you check in at 11PM and someone asks, you could show them the voucher and explain that you would be happy to stop in the next day and show them the pass after you had exchanged your voucher at guest services. I wouldn't worry about it at all.