I guess it was bound to happen sooner or later. After 600+ transactions, I picked up my first negative feedback on BrickLink recently. It isn’t the end of the world but it would have been nice to know there was a problem so I could do something about it. I’ve made mistakes before and will likely make them again. It happens. How a seller handles a mistake is really what matters and I don’t have a lot of respect for a buyer who doesn’t give a seller the opportunity to fix a problem. If I make a mistake, I do my best to correct it as quickly as possible at no additional cost to the buyer. I’ve even ordered missing parts from another store and shipped them to a buyer if I didn’t have them myself.
In this particular case the buyer never told me there was a problem, I just noticed it on my feedback page. I don’t deny that I made a mistake, shame on me for not checking the set again for completeness. I would like the chance to fix it though.