I get that a lot with online vendors for my computer projects I do. I have run into ordering parts for liquid cooling setups, and they show the parts in stock, and I have had them e-mail me telling me the parts are on backorder.
It's pretty darn frustrating especially if you need the stuff right away.
I feel your pain. Most of the time now, I call the vendor and ask directly if they have the part in stock before i make the order. It's a PITA, but at least I know I will be getting the parts.
Most if not all tracking systems are sh*t, they don't update and can be several days behind.