Found on a forum
>>Also wjhat is the nice boat treatment? When a video gets deleted and its replaced by a boat and some lady talking?
>What you are seeing is the current video for the "video has been deleted by the uploader". When a video is deleted by the uploader, a flag is set and it plays the current deleted by user video instead.
That sounds about right. There was no reason that nicovideo would have deleted it. Perhaps the uploader uploaded a higher resolution upload and deleted the old one?