Whether you are providing a product or a service, this is one of the most important things you must remember. Your clients don’t care who didn’t show up for work, who’s sick, what shipment didn’t come in, or any of the other things that could keep you from delivering on your customer’s expectations.
If it’s a supply problem, find a different supplier. Your customer doesn’t care if your price is 10% lower than the guy down the road if you don’t have any in stock but the guy down the road does. Though your customer may feel empathetic for your employee with the flu, they would rather call the other company with a whole team of people that could help them immediately, than sitting around hoping your one employee will get well soon.
Take a good, hard look at your ability to deliver to your customers. If you have a delivery problem, get rid of it. Now.