By printing an asterisk in the upper right corner of price tags, Costco lets its customers know that the item in question is in short supply or the last of the supply in the store.
It doesn't necessarily mean the item is being discontinued, but it does mean you might want to find out when or whether the item will come back and load up your cart accordingly.
To know if and when an item will be restocked, visit the customer service or membership counter and ask. They might even be able to tell you the exact time it will be replenished.
Costco doesn’t keep a constant stock of items because buying a limited amount and rotating certain products helps keep the prices on all of the items down throughout the year.
Additionally, it does not make sense for the company to keep certain products on shelves at all times due to seasonality. Not every item will be in demand all year long.