It doesn't even seem fathomable that they could allow this to happen -- although many postings have blasted their computer capability and slow speed for booking online. I'm glad they corrected it -- but it would have been awful to arrive day of and find that out! That's why I print duplicates of every confirmation and email LOL..
We arrived at port once and the told us we didn't have a reservation. I thought I was going to faint and/or throw up. We had done online check in, had all our excursions booked, etc I KNEW we had a cruise. I have to say that the initial people we dealt with were not all that helpful or friendly. They kept insisting that we had canceled and that our credit card had even been credited. I had all our paperwork and we even got on the phone with our cc company to show there had been no credit. Eventually they said our reservation had accidentally been cancelled when someone else on our cruise had cancelled their trip and their cc was credited. Honestly this seemed like a really flimsy excuse since that meant they didn't credit the card on file for the cruise and we didn't receive a cancellation confirmation email but whatever. They did find a room for us (a slight upgrade) and once onboard we got a Lithiograph and my son got a stuffed animal for our trouble plus a call with the head of guest services three times during the cruise just to check on us. So it does really happen, and I think their customer service is a little shoddy when you first find out (they just kept insisting they were right despite all our documents and the credit card facts). I don't know what they would have done if it was a sold out cruise.