The deal is when then clutch fails it just slips and slips, no popping out.
"Poppin out" seems more of a synchros bad. Is there any asbestos smell? and I mean a lot similar as when someone drives with the e-brake engaged.
A very bad clutch the car will not start. Another question, Does the gears go in when the car is not running? You are suppose to clearly hear the engagement on every gear. A bad flywheel will be not engaging in any gear, but once in that gear will stay there, and not kick out. Mostly on flywheels that are very worn on performance clutches and there is too much gap or an incorrect [wrong clearance] fw (Dont ask how I know, je je).
I would say is more a bad trans.