I am also in agreement that if they had their gun loaded, the it was capped and on halfcock. To me it makes no sense to not have it capped. I was thinking of the little pocket guns. When at the gambling table, are you going to pull that derringer out of your pocket and cap it before pointing it at your problem?
Now having something to help protect the cap was probably done, but not widespread though. I do have a leather frizzen cover on my flintlock rifle. It is easy to flick off when needed. But I don’t think that I really need it though.