Oh, where do I begin?
An undetonated blasting cap is not filled with cotton. It is filled with three layers of explosive, starting with something the hot filament can ignite followed by a chain of more powerful explosives ending with RDX or PETN at the tip.
If it had been used to set off that explosion it certainly wouldn't be an undetonated cap.
If it was at the explosion site and flung 1.4 miles by the explosion, it would have self detonated.
Caps can be safely handled. Don't squish them or get them hot.
There may be cotton inside the epoxy wire seal; however, you can't see that if the case is intact. If the case is not intact, than the cap definitely has been used.
That’s what I thought.
If it had been unused it would be sealed..............