i'm not a fan of this translation into english because it just sounds a little odd to me. but perhaps a native indonesian speaker can lend some light on possible context here?
the use of the english word 'part' brings to mind for me:
either 'spare parts', which i believe is 'suku cadang', but does 'bagian' also mean something similar?
or 'role', such as a part in a play, which i think is 'peran', but again can you use 'bagian' to indicate this kind of part?
otherwise i'd be inclined to say it differently in english, such as: 'where is my piece?', 'where is my section?', 'where is my share?', or just 'where is mine?'. hopefully these suggestions can be added to the database of acceptable responses.