Without the context, "missed connection" may be interpreted in two ways: 1. a connection you wanted to make which failed to work out - like a telephone call. In this case "missed" means a "failure", and "connection" a communication channel. 2. an old relationship that no longer exists which you wish you still had. Like, if you lost contact with someone who used to help you a lot, you would miss him/her. Here, "missed" means "you're sorry it isn't there anymore" and "connection" a relationship. That's my best guess. If you need more concrete answer, you should provide the context too.