Finished insulating my shed studio yesterday... the difference is night and day.
I used fiberglass batts and sealed all the gaps. Now my kiln heats up faster and holds temp steady. It was a slog, but so worth it for consistent work. My hands are sore from all the stapling, but I'm thrilled with the result.
Was it one of those times you were trying to hold something dumb in place and the gun just... slipped? Because that's a special kind of regret. The sound is almost worse than the sting. Bet your friend learned real fast to keep ALL fingers clear of the business end.
Did you earn a black belt in staple gunnery after that? All that pain better mean your kiln is now PERFECT. Seriously though, solid work paying off like that.