how can i fix my dyson dc-04?

I recently brought a second hand dyson to find that the main fan belt was broken. Being a do it yourself guy i stripped it down. When disasembling the vacuum a small plastic pin (odd shaped) came out from where the small belt that turns the bottom brush housing is. I dont know if it needs it and can not find where it goes. Does anyone know of this part (its white).

Mark
February 2007