As a matter of fact, it exists. However, it is only used in rare ocasions, i.e. quisiera que vinieses (vinieras) a mi fiesta.
You can see it in this link about halfway in the page, some lines above a phrase in red, and some lines below:
Enlace a gramática He dedicates such few attention to it for it is a rather unusual expression.
[ 08-24-2001: Message edited by: Ignacio ]