Soldato
if its in stock when you place and order and choose next day delivery as the option then with any other retailer i deal with you should get exactly that. Not a lucky draw to wait and see if you are lucky for the next shipment that comes in at the end of the week.
You still need your payment to go through before as well to have the stock assigned even at other places. For whatever reason that wasn't case here but that really means that you hadn't actually got any of the stock they had because others brought the stock with payment that went through without manual input.
I've had same from other places before.