Our webshop marks it with a green tick under the product name, or on the product data sheet, above the price, if the product is in stock, otherwise, next to the yellow clock icon, there is the inscription "Out of stock, available to order".
The warehouse display is informative, as our webshop and our store sell from the same stock, so in the case of a webshop purchase, the product status in the confirmation email is relevant.
For most products, the average order time is 7-42 days if not in stock when the order is placed. Unfortunately, we cannot say any closer, when it will arrive.