Stuck Clutch - Piston not returning to rest?

I left my car outside overnight on Tuesday and when I got up I had some troubles getting moving. I wasn't sure what was happening but it turned out to be the parking brake being stuck due to the cold. I drove about a block and turned around when I realized the brake wasn't going to unlock. About five houses down from me the car stopped moving. The engine was redlining but no movement whatsoever. Essentially no power going to the drive train even though the car was in gear. Couldn't go forward in first or back in reverse. After the outside temperature warmed up the parking brake unfroze and is now working fine. Unfortunately there's still no power going to the drivetrain. The clutch depresses but feels like there's minimal upward pressure when I take my foot off of it. With the car running and without the clutch engaged I can shift into all gears. The same as if I had my foot on the clutch. I believe there's a piston that the clutch pedal pushes against that is stuck and not returning to its resting position. Before I climb under the car and start hitting things with a hammer I was wondering if anyone has an alternate diagnosis. If my diagnosis is okay I'd appreciate links to some pictures or diagrams of where that piston is located on a 2006 Ford Fusion with the 4 cylinder engine.

HI, you may have burned out the clutch.

OK, The "piston" you are talking about is the Master Cylinder. It pressurizes fluid then goes to the Slave Cylinder to release and engage the clutch. Go to online parts stores to look at your parts. You may just need to bleed and flush your hydraulics, You can tap on the Master… In the engine compartment drivers side to the right of the brake booster. If you have an external Slave, you can tap on that too.

It could be that the piston in the slave cylinder is not returning. There could be water in the clutch hydraulic system and freezing so that the slave cylinder can't return to normal position.