how can i fix my spectroniq pdv-70x portable dvd player?

my dvd player displays "wrong disc". i took the top off and discovered a tiny white part that had fallen off from somewhere. i know the general area where this part goes but im not exactly sure where or how it fits. can anyone help me with where it goes or show me a diagram of the inside of this unit? this part would be put somewhere in the area that the motor and and laser are located so its a very small area.