Welcome to the forum.
I'm not really sure what you are asking and I assume that English is not your native tongue. So with that being said...
It would be unusual but not unheard of for a 2009 GS to have had it's engine replaced. If you suspect that it has been replaced then I would just move on to the the next bike. There are too many clean late model GS's out there to get one with a questionable history. Good luck.
Oh, and fill out your profile dammit.