If the year-old charge was a fresh load down a clean barrel, then I would agree, moisture could have been drawn through the touchhole or the lubed patch, resulting in a possible mess in the breech area. This would require some serious time with 0000 steel wool, because pitting may well have occurred in those bottom few inches, but the barrel will still function. The remaining pits will make future cleaning a troublesome time for you because the jag and cleaning patch will want to grab in the area on every trip down to the breech area.
If the year-old charge is a load pushed down a previously shot and uncleaned barrel, the problem is much more severe. That old black powder residue and accumulated moisture has worked some evil magic from the muzzle to the breech!
If that is the case, don't send the gun to me to bury, just remove the barrel, and bury it yourself.