Don’t mean to sound rude, but thinking it’s not loaded and knowing it’s not loaded are two different things. I once traded for a Thompson Center Hawken barrel and the guy I got it from swore it was unloaded. When I dropped a ram rod down the barrel I knew immediately it was loaded. So, I replaced the nipple with a grease fitting and pumped grease into it with a grease gun. Out came a round ball, a charge of powder, another round ball and another charge of powder! He acted surprised and embarrassed.
I’ve bought several used muzzleloaders that were supposed to be unloaded but actually weren’t.