LONG READ... Sorry

Okay... here it goes... temp gauge inside dash no longer moves... multiple sources have suggested replacing the coolant temperature sender. Unfortunately I'm unable to locate the lil gem.... as far seen on a video and pictures the sending unit should be just on the thermostat housing or just slightly off.. now.. I see a threaded Allen screw filling a hole on the housing where this coolant temperature sender should allegedly be... and the wire that I've seen connecting to the so called unit is traveling north above the coolant temp sensor... only to be connected to something I'm unaware of few inches above and just prior to the temp sensor... so I ask.. for anyone familiar with this.. should there be a temp sender in the housing (which I've seen via video and pictures) where the Allen plug screw is?