sometimes small shops can be inundated with (sudden) orders....and get wiped out.- they are probably as disappointed as you are that they could not fill your order- but are also probably amazed how quickly everything went!
it's like the resturant that runs out of a special long before closing time one time- and have left overs another---you just never know-
it sounds as if they are (trying) to take care of their customers in a good way.