As a question, are you saying you didn't receive the mail at all?

Because with Vet items, the time I had en error, the mail had a potion that I couldn't grab instead of the item it meant to be. Are you sure you maybe just opened it up and didn't grab the item, and is just sitting in the open tab of your inventory?

Also, Nexon's much worse. Their report system doesn't even work, and that's intentional.