Reference muzzle loaders left loaded.
In general, rifles were very rarely left loaded, though nothing should be taken as certain. But rifles were used for hunting and usually when the hunter left the woods, he fired off the charge before heading for home.
But shotguns ALMOST ALWAYS were left loaded. In the old farm houses, the shotgun stood by the kitchen door, waiting for the squalling and screeching that signalled a fox attacking the chicken coop. The farmer grabbed the gun, reached up to the top of the kitchen cabinet for the caps and headed out to take on Mr. Fox.
When the old folks passed on, and the farm became a housing development, the old gun was kept by the family, few of whom knew anything about muzzle loaders. Several generations of kids played cowboys or soldiers with the old gun, never knowing it was loaded. Sometimes they put toy caps on the nipples and sometimes the old gun went off with results either tragic or comic, hopefully the latter.
So a good rule is to ALWAYS treat any muzzle loader, no matter how or when acquired, as loaded until you KNOW different.
Jim