Just Be Friends - Where can I find it?

so far, all the "just be friends" by megurine luka on the internet are four pages long and clock in around at two minutes: the abridged version. the full piano version that's around 6 mins long is on youtube, so how come there's no sheets for it? I mean, there's no way someone couldve just played that without any music so there's definitely an original full copy floating around somewhere. I really wanna find it and finish playing it!