You are right, it would have been courteous for him to have given you notice in advance. If he did indeed get things going great with his wife he might have wanted to tell you but felt unable to do so. It's not easy to break things off with people so some simply do nothing, that may have been what he did but that is only one possibility.

If you do talk to him again you should tell him what you really feel, not saying anything can cause trouble in the first place.