Were are the majority of the philosophers in the novel from? why might this be? who seems to have been left out or forgotten? wHY

Most are from europe, but that is because the book is dealing with the history of western philosophy outright, if this was Tzao's world then most would be from elsewhere. In a certain sense your questions beg the answer: eurocentrism, but that is a simple out, because though overly explored there is no less valdity to the western cannon. There is no conspiracy to leave major names out just because it focuses on a well treaded path that has western roots. One could trace a path of modern thought through the intellectual leaps that pertain to the history of Mathematics and find authors from europe, asia, and the middle-east and then ask why the Americas had been excluded. One might just lose the whole point of philosophy by focsing on the identity and ethnicity of authors and not understanding the validity of ideas. Does it really matter who first postulated that 2+2=4 if in the end that tautology is valid? I think therefore I am, was first published in Latin written by a frenchman, does that mean that a South American woman cannot find a universal meaning in the undestanding that thinking presupposes existence?