It's not unusual for the firing pin to protrude from the breechface when the slide is locked open manually. However, as the slide comes back forward, the "sear" picks up the firing pin lug and holds the firing pin in place as the slide then continues forward. That will pull the firing pin nose behind the breechface. When that happens, the firing pin safety will engage which prevents the firing pin from moving forward far enough to fire the pistol even if the engagement between the firing pin lug and "sear" fails for some reason.
By the way, during a normal firing cycle, the firing pin will be retracted by momentum when the slide hits the end of its rearward travel. If you examine the breechface of a gun after the slide locks back after a having been fired (as opposed to having been manually locked open) you will not see the firing pin nose protruding from the breechface. You can duplicate this effect by vigorously racking the slide with an empty magazine in place.
