There's also a chance your buddy left the nipple hole open during his stay in the woods. When you walk around, you should put a plastic car tire air valve cap over the nipple & close the hammer. While seated, place a live cap on the nipple & leave the rifle at half-cock.

Always remove the nipple before getting up from your seat or when tiredness occurs. Never have a capped rifle standing against anything nearby.

Also, make sure the powder gets down in the nipple area when loading the powder. Also check for a worn or mis-shaped nipple head & make sure your powder is dry. There is a slight chance his lock assembly and or trigger assembly is worn. Check for wood shreds & shiny, silvery, worn spots that would normally be black.