My Secret Order Mix-Up at Work

So yesterday was hectic. I had a line out the door and got this rush of orders that all looked similar. One customer ordered a latte with soy milk, but the next one said they wanted theirs black. And you know how it is in coffee shops, everything just starts to blend together sometimes. Anyway, so there was this guy who was regular, he came in late morning and I got his order mixed up. He asked for a black latte with no syrup or extras, but when I handed him the drink, it had been made as a vanilla latte. And just to top it off, I used almond milk instead of soy! I was so embarrassed! I tried to apologize and fix it right away, but he just said 'No worries' and walked out with his drink. But ever since then, I've been wondering what he thought about me. Did he think I'm really bad at my job? Or maybe he's mad and won't come back? So, have you ever messed up a big order like that? How did you handle it?