pushrod problem

[SmokeShadows]

so my issue is that I suspect I over revved the engine one time on a "journey" and it started to make a horrible ticking clicking sound, I assumed it was a lifter tick but it was louder then it seems it should have been, I turned it off for a couple hours and started it back up to drive 20 miles home and same noise, the ride was rougher then usual, I got home I parked it and opened the valve cover which I suspected contained the problem and came across one of the cylinders rocker arms weren't even on the push rods and one of the pushrods was almost all the way in, the bolts weren't falling off , no excessive wear or obvious signed of failure, now iv done much research with no luck, the questions are: what's causing the pushrod to fall all the way in? is it possible for it to jump out of place? can I just replace the lifters rods rocker arms etc? any information is much appreciated i know i may be asking alot but it seems like it was fine one second and one rev later tick tick tick oh and the motor is a sbc 350 71 gmc 57xxx miles edelbrock intake/carb