In my mechanic days I called engines with my own terminology 1. no interference engines (if valve drive mechannism chain or belt stopage occured no valves would hit each other and the piston would not hit a valve), 2. single interference engines (valves would not hit each other but the piston would hit a valve) and 3. double interference engines (valves would hit each other and the piston would also hit a valve). MG and Triumph engines with pushrod valves in a bathtub cylinder head were no interference engines. In some other engines, the valves would not hit each other but the piston would hit a valve. Alfa, Jag, and most exotic engines like Ferrari and Maser engines are double interference engines. If the valve train fails the valves coasting to a stop can hit each other and worse, the piston can hit one or both valves.
But when this happens there is a catistropic failure of the valve/crank drive mechanism and this is always accompanied by very loud, sickening, and expensive noises. Valve heads can break off and impact the pistons as the engine winds down to a stop. And pistons can crown valves extending into the combustion chamber, putting holes in piston heads and the broken off valve heads can be driven like knives into the bottom of the cylinder head. But again, all this is accompanied with loud and expensive noises. Since saniei did not mention a catistropic engine failure, I cannot figure how he could instaintaneously go from a running engine to a zeor compression engine without accompaning failure noises.