There is no spring behind the pedal to fall out in the way you describe, there is a coil spring inside a plunger which acts on a cam to give control loading, in the first 50% of the stroke it will return the pedal to the top position, in the bottom 50% it gives assistance, if there is no fluid pressure acting on the piston it will push the pedal to the floor and hold it there.
Nobody has asked what gearbox the OP has, if its a 5 speed with external slave cylinder then its not a gearbox out clutch replacement job, if its a 6 speed with concentric slave cylinder then it is.
Nobody has suggested checking the master cylinder, they can and do fail, there is a powerfull magnet that operates a reed switch to tell the ECU that the pedal has been depressed, this gather abrasive metallic clag, from where I know not but it can score the cylinder also the piston pressure seal can fail without any leakage.
9 times out of 10 is the O ring on the later 2 piece concentric slave cylinder becoming abraded through vibration and allowing air to enter the system without ever leaking a drop of fluid, the physics of it are beyond me because it is always under hydrostatic pressure but that is the failure point.
Clucth action can be restored simpy by opening the bleed nipple and closing it as soon as fluid dribbles out, you dont even need a spanner, it is done by hand, you will probably find the pedal action iffy after some while, whatever you do never lift the pedal up by hand or with your foot, that will 100% bring in air through the O ring.