I had the same problem on Saturday when I logged into my account to see the waitlist letter that they posted in April but the link vanished and I told myself: "Where did it go??"
Well the next day, I checked my e-mail and I was accepted to Columbia from the waitlist and then it told me to return to my account and I saw that in lieu of the waitlist letter, there was the acceptance letter.
Not to get your hopes up, but I just want to address this problem for all those who are curious. My guess is that they are reviewing you guys if they do that to your account. Remain optimistic.
