Those things happen when you get distracted during loading. Make it a practice to never answer a question or acknowledge anyone in the middle of loading. It's no insult to say, "Be with you in a second.", finish loading and THEN answer the question.
How do I know this?
Was cleaning the ROA one evening when the wife dumped part of a hot soup pot on the kitchen floor. Took an hour to get it all cleaned up and of course I helped. Went back downstairs, cleaned up the work area, put the guns away and went back upstairs. Next day at the range I was demonstrating how to load the ROA for some newbies and one of them mentioned that there was black powder all over the floor and my shoes. Forgot to put the nipples back in.
You'd think you could eventually live something like that down. Believe me, ain't gonna happen.