Temperature gauge issue

[merrittr]

Was driving my 1996 mazda protege 1.5L DX and noticed the temperature gauge was still at cold theis is after 15 min of driving. the upper rad hose was cool and not full of water
does this sound like a simple tstat failure or would it be a sensor?

 

[hornsfan10609]

Gotta be the thermostat if the upper hose is still cold.