I did the exact same thing many years ago...was pinning up a hem for someone and had a pin in my mouth. Must have breathed the wrong way or something and one went straight to the back of my mouth. I couldn't talk and was too scared to move. The lady I was pinning for had no idea what had happened as I wasn't game to try to tell her. Luckily I was able to reach it with my fingers and remove it. Never put a pin in my mouth since that day