How did the prince get the Amulet in the warrior within

unfortunatley, I'm not sure, in fact, I don't even think ubisoft actually came up with it, if only we could ask them... Either way, warrior within is set 7 years after the sands of time but he is not in possession of the amulet in the forgotten sands as he uses the powers of Razia the djinn to alter time. He somehow must have gained the amulet after the forgotten sands, but you probably worked that one out yourself...
Update! If you look in the game manual for warrior with it reads in "Time Powers" the following...Thanks to the amulet Farah gave him at the end of the sands of time, the prince still has the power to control time" this is contradicted in 2 ways
1) just like I said about how the prince does not have the amulet in the forgotten sands, set before warrior within but after the sands of time.
2) forget what I said about him aqquiring the amulet after the forgotten sands, and number two is that Farah is never shown giving the prince the amulet on the cutscene at the end of the sands of time.

:)