Thermostat, chasing cooling issues in my 2004 4.6 liter Ford V8

EC6AE2E1-8CAB-41F9-8C74-684EB30D0952.jpeg 2004 Lincoln Towncar.

there is a rock AND a screw holding the thermostat open!

I know every old timer here can one-up-me, but I would not have believed it if you told me-One screwed thermostat!

replaced the radiator fan & control module (went ahead anyways as the car is almost 20 years old, replaced the thermostat, and the ECT Sensor is next. Car only over heats with A/C on sitting at lights, or sitting in traffic long enough. It is hot out. Have already conducted a drain and fill while in Automotive class (they promised me a flush, no such thing occurred). The car has a new radiator.

would love to hear some exotic stories added-maybe suggest a specific thread on the forum.