You can get that too. The catch is that you can't get the Dew's Yarn or the Wizard's Loom if you had WFC in your inventory when you SAVED -- doesn't matter if you've since sold the WFC. That's why you can get two sets of WFC.
The Staff of Thunder works the same way, I believe.
It does for the Staff of Thunder. That's the method 9 out of 10 people use to make money in this game. --- "If drumsticks are for playing drums, you'd think breadsticks would be for playing bread, wouldn't you?" ~George Carlin