Good deductions, 54Ball.
I think we could hammer this around for quite a while. Unless we were over this guys shoulder the whole time, all we can do is speculate as to what, if anything, he did to facilitate the incident.
One thing I did notice from the pictures. If you look at where it split, it looks like (Murphy's Law?) the touch hole was drilled right on, or real close to the weld. Could the barrel have pulled free of the breach plug after the barrel split open? Or even if it were dropped afterward? At that point, there wasn't much holding it all together.
If any of this is the case, and if there was any obstruction, be it a paper wad or fowling, it is disturbing to think that the obstruction was stronger than the weld or breach plug-barrel threads joint.
I have seen quite a few men pull the trigger and get only the pan flash. In the heat of it all think it went off and load again... it happens, and any properly manufactured barrel should be able to withstand a double load.
But what ever did happen, IMHO, it all boils down to the musket itself and not operator error (Even if he was a Lobster Back).
I think we all agree that this is a relatively isolated incident and it doesn't necessarily cast any aspersions on any reputable dealer or his wares.
After 20 years as a police officer, I've seen Colt and S&W revolvers come apart, Glocks explode and barrels split.
But,instead of dancing around "who made it" or "who sold it" anyone owning an Indian musket deserves to know for their own peace of mind. This way, if you own a musket from the same wholesaler you can simply take it to a gunsmith for inspection instead of worrying every time you squeeze the trigger.
Leaving the story like this is like being told your girlfriend is "A little pregnant"
Just my thoughts, and I wish the gentleman well.