Jack could probably word this better (he's good at such things) but I would think that they might have uploaded the trailers to their server and somehow that was found.
I'm probably off by a million miles, but I was jsut taking a shot in the dark there.
You're actually right.
Many sites upload content, such as trailers, and hide them to prevent them from being seen until the time is right. E, every once in a while, leaves clues for others to find, such as with the UltraGaff teaser.
Now, if I were to look for the UltraGaff teaser, I probably could not find it. However, if I use the search function, it shows up.
What I suspect happened is that somebody forgot to conceal the trailers properly, when they were testing it to check if it works, et al., as it is being release later this month. As a result, a person, who exploring the site, accidently embarked upon it.
And now it's been download, streamed, etc., for many to see.
Cheers,
JTM