Inventory available for pro purchase is fluctuating constantly due to retail demand. We do try very hard to keep inventory updated, but because our manufacturers drop ship and fill pro orders after retail orders, occasionally some of these are canceled before being updated on the site.
You should receive a cancelation email notification when an item has been cancelled, where you can view the cancelation reason. You will not be charged for the item, or shipping the item.
If you did not receive an email confirmation for your order, or you don't see your order in your order history, it's possible your order did not complete correctly. Please reach out to customer service to verify your order.