I would not stress on it too much. For me, this happens almost every time I meet someone new. And truthfully, this situation will occur again and again. The quicker you can accept it the easier it is. If it happens, it happens, that's just how your mind functions. Excuse my French, but fuck whatever people think at you. Trust me, I have received those looks while I'm in the middle of a block and it truly does suck. It is what it is. Keeping a short memory with a stuttering incident is a very important thing.