The only way to make sure the part that pin holds has not come loose is to pull the valve cover and check. It will be easily seen and you can wiggle it to see that it is still in place.
That being said, I pulled the valve cover off an old engine I have in the garage last night and the 'umbrella' guide that pin secures was very tight in there.
I doubt it would drop with the pin pulled out, so long as there was nothing else going on, like starting up the engine, or what ever.