Was at range today, I had a missfeed. Cleared weapon and could not get the slide to forward in place. Messed it for a while.  Came home to realize I had lost firing pin stop. So question is. What did i do?  What may have caused it?  Common occurance?

I know what caused missfeed. Crappy Lawman ammo that my colt didnt like right out of the box. It is model 80 series thanks for the input.

Sounds like it cracked and fell out, At least the FP safety kept you from losing any other parts. It does happen occasionally but it's not really common.

Another possibility is the firing pin spring is getting weak and/or the firing pin stop is a very loose fit in the slide.

If so, under recoil a loose FP stop can just drop out of the slot in the slide.
The "fix" is to buy and install an over-size FP stop.
This should be a snug, but not too tight fit in the slide.

Back in the days when special over-size parts were not available, Jeff Cooper used to recommend installing a small screw in the stop that entered a small hole in the slide to lock it in place.