Exceptionally minor bug. The "Practice Spear" that Hernmort sells (and possibly other weapons he sells too) only contain one of each stock, rather than unlimited. So if one were to desire two practice spears for say, two people to practice with, one would be hard pressed to find a second.
I know at the very least that this isn't the issue with his light hammer and clubs. (Both Practice varieties, I mean)
Also, Speckard either doesn't sell longswords, or he was out for the same problem.