sounds like it to me.....to check it ...fill the master cyl...have some one pump your clutch and see if its leaking..if not it should be moving about an inch if not then its in your master cyl
sounds like master to me, ive had a slave go on me and the pedal still came back up
maybe his pressure plate took a dive
sounds like what mine did after i had to replace the slave cylinder, ended up having to change the master cylinder too .