It just happens sometimes. That's why we have to do all the research for each vacation we plan, because what was true for one trip might not be true for the other.
From what I know, the inventory available when you call can be different than the inventory available online. And the inventory for packages can be different than that for room only. So if what you want is still available online, you might try anyway.
And if you're booking HoJo, remember that there's a 15% discount just for mentioning taht you're a user of the disboards (you do have to call the Anaheim property directly, during business hours on Pacific time, AND ask for "in house reservations").