yes, and thats why in my opinion sengoku obeyed shanks's every command at marineford. He doesn't want shanks to tell the world about the truth that they found at raftel--which will make the world government look bad . I feel like raftel has the world government's dirty little secret which is why they arrest any pirates that try to go near it.
if we logically thinking about buggy's character we can easily say that he indeed knows what one piece is but it's just not worth it. if he didn't know what it was he would only want to have it even more. but since he knows what it is and that mentioning about it or going for it will be too troublesome. we also know that buggy thinks logically and wouldn't risk his life for the sake of treasure. he gave up on underwater treasure as soon as he became a DF user and threw away the treasure map or lost it and didn't care about it.
Ch 17: Luffy says he will be the Pirate King. Buggy replies he Buggy will get all treasure in the world. One Piece? Truthful translation?
I think Buggy and Shanks know what One Piece is. They were on Roger's ship for a while, they'd know what One Piece is. I'm guessing Buggy doesn't have the guts to go after the One Piece while Shanks doesn't care or doesn't want to get One Piece since there's no meaning for him. Could also be his way of testing or placing faith in Luffy.