I broke the sensor on the bottom of my radiator, whats it called?
 

At mazdatrix there is a water sender for 44.10 and then a water thermo thing for the rear housing for 29, Im guessing its the $44 one.

Is it the one with two prongs?

Water temperature switch. Used by the ECU for emissions. Not anything to do with your water temp gauge.

Normal driving, with it disconnected you will not notice a thing. But...it will be effecting your acv/relief solenoid. Get another and connect it up.

It screws out.There will be no loss of water from the radiator. It just senses the heat from the radiator, not directly from the water itself.

I don't see the part on the Mazdatrix site. The items you mentioned are not the device. Call Mazdatrix and explain the location. They can get you one.

P.S. Get one from the wrecking yard.