Woo. Problem resolved here. Kitty woke up this morning, "asked" to be let out. He went outside, looked around and then headed out in a very purposeful manner. Not running scared mind you. Just looked like he (she?) had some intent behind his course. And no, I didn't slam the door behind him or anything.
It remains to be seen if he will return.
He almost sounds like the cat my neighbors had when I was a kid. He started sitting on our windowsill one day so we let him in. Next thing you know he was spending a lot of his nights just sleeping at our place and then we'd let him out again when he wanted to leave. We had all the benefits of having a cat with none of the fuss!
Here he is sleeping on my bed.