Plug or hose came off back of block

[f00g00]

Today on the way to work I lost all the water in my car and didnt notoice there was a problem till I heard the knocking sound from engine runing too hot. I shut it down got a ride to work and looked at it after work, There is some piping behind the head that goes to the heater valve on one side and the other was open with nothing on it. When I poured water in the radiator it poured out of the pipe just as fast. To get home I cut the top heater hose about 3 inches and shoved a spark plug in the upper hose and made a plug for the pipe behind the block with the cut off end with another spark plug and clamped them. Made it home with no apparent engine damage.
Now my question is, what goes there? There were no hoses hanging off and by the looks of the diagram in the TSRM it seems there is a block off there.