This is very strange and I cannot apologise enough for this happening.
Our website is updated in real time. It should not be possible to order something on the web even if somebody has placed an order for the last one just minutes before.
As a safety net, we always keep one product in stock as a "buffer". This should always ensure that our customers are not let down.
I am led to believe that what happened here was a case of an incorrect stock record. When our shirt packer went to pull the shirt from its normal location, it was just not there.
This is extremely annoying for us because we have lost a customer (and we never like to do that) and even more annoying for you because you have been let down.
I can only say that it happens very, very rarely and I do apologise wholeheartedly. I started this business 20 years ago and it pains me as much today to let down a customer as it did back then.
Best wishes
Nick Wheeler