Express Oil Change Irondale AL Engine Flush, and Thermostat...turned into needing head gasket....$1200 difference. Irondale, Alabama

 
 I was on my way home from the store a couple of nights ago, and noticed my temp gauge almost about to go into the red.
I immediately pulled to the side, and cut the car off. Checked the oil,all full and good. I waited til it cooled off, checked the water in the radiator, topped it off with 50/ 50 then drove it home, (about 2 miles),
while watching for it to overheat, it didn't.

 I talked to mechanics that have been in the business for years.Told them exactly what my car was doing:

 Ran hot, I cut the car off before the gauge registered in the red.I let the car cool off.
I started the car, and let run til it heated up.The top radiator hose was hot, the bottom radiator hose was cold.
Rusty looking water was running out the overflow.

 There was no water in the oil, there was no oil in the antifreeze,but the water that overflowed from the radiator was rusty looking.

 They said it sounded like a thermostat.

 I took the car to Express Oil change in Irondale AL. I told them EXACTLY what I wanted done. I wanted the engine flushed, and a new thermostat installed. The guy behind the counter told me it would be $270 and it would take about 3 hours. 
 When I called him back, they said I had a BLOWN head gasket! I asked them if they had changed the thermostat, they said no.
There was NO indication of a blown head gasket before....no tell tale white smoke from the tailpipe, no oil in the anti-freeze, no water in the oil, no steam from the block, nothing.
 When i picked up the car, it was still HOT.
 I know that before I took it to them, I had to let it run for quite a while before it got HOT.
There was no reason for them to run it until it got hot.

 The cost to change a head gasket is $1500.

 I told them just charge me what i owe them, so i could get out of there. They charged me $20.

OK, I got the car back home, let it run til it got hot, the water is circulating in the radiator, the bottom hose is hot... The oil doesn't have water in it ( on the dipstick), the radiator doesn't show to have water in it...I checked the tailpipe, no water vapor.....
 
 In short, it doesn't need a head gasket, it doesn't even seem to need a thermostat now.

 So what were these guys trying to pull??? Maybe charge me $1500 for a head gasket, that they weren't even going to put in?