The refurb stores on the various national websites reflect live inventory. There isn't an endless supply of any refurbished machine, so items are deleted when they go out of stock. Once another is available for purchase, it will again appear. Sometimes a few products will disappear, and [more rarely] all of them will.
If you're wanting to purchase one, I'd suggest watching the refurb section with a regular frequency so that you'll notice when it's updated. They'll be back.