Covershield They took money and listed an item as shipped and 4 plus days later they cancelled the order without reason California

I placed an order with them on Ebay. They accepted the order and send a confirmation fron Ebay and Covershild that the order was shipped. They even included a tracking number. 4 days later they refunded my payment without explination. I called them the next day (the notice came at night) and they said they were out of the item. I ask why it took 4 plus days to notify me. They had no answer. I now will not be able to get a replacement item shipped to me by Christmas. 

I do not understand why Ebay would allow a company to sell items they dont have or why a company would do such a thing. I would warn others to not do business with such a company. The practices of this company are fraudulant and they do not care ablout their customers nor does Ebay seem to care about this type of practices.