What's the history behind this situation? Did it just all of a sudden stop working?
Parts manuals aren't free. Your dealer can order one for you
If it's a break or disconnect there should be a pool of fluid, unless it's a quick disconnect and it should be easy to find.
My tractor has a push-in yellow metal tab that locks the joystick. It's toward the lower end of the joystick facing the front of the tractor