Bumping this old thread. I just experienced the EXACT same pop and now have a lot of free play in my clutch pedal, probably and inch to an inch and a half.
Clutch engages fine, drove all the way home from work tonight with no problems. Just concerned about the "pop" and free play.
Also have an Exedy Stage 1 clutch and 06 wrx flywheel.
Any input, reassuring comments or advice on how to fix this free play greatly appreciated.