Planets aren't stationary.
And if a planet can't be found by NASA, then how the heck did some conspiracy theorist nutjobs find out about it?
But lets say that there is such a planet. You still haven't explained how it's supposed to go from "behind" Jupiter to Earth in just three days. 
The whole thing just doesn't make any sense at all. I could go on and on about why it just... Oh my god dude... What the heck?! The physics of it just makes no sense!
False authority fallacy?
For some time I actually wanted to be a physicist when I grew up.
ANYWAYS...
I know what you're talking about. Apparently there's this planet with a highly eliptical orbit of 3600 years called "Niburu", and it hosts an alien race which actually aren't aliens because the engineered us, and they're going to fly by and turn us into slaves... Combined with Nimburu colliding with us... Combine with the entire Earth flipping over 180 degrees... Combined with all the planets in the solar system aligning with the sun and the dark rift in the center of the galaxy destroying the Earth... Combined with solar flares burning the Earth to a crisp.
I've seen models. Jupiter and the Sun are pretty big. *Bob holds his hands up to show the size of these bodies.*
The rogue planet could be travelling really fast. And then it will slow down immensely due to the Earth's gravitation field and draw out the the impact in slow motion. Perhaps the Sun's polar shift will be the deciding factor? Yes. Yes, I think the Sun's shifting poles will slow down the rogue planet's gigantic velocity. It's very advanced physics. We can't comprehend it. But the Mayans could be they were an ancient mysterious civilization. Ancient civilizations know many things that we don't. Because we have science blinding us.
I see you're agreeing with me now. Finally coming around to... the Truth.
Maybe it's Niburu. Maybe not. We could always save that for later if it's not.
I'd watch out for the worms on that planet too.