Quote from li5445: Go
Are you sure in this for 100%? It is very important for me and I'm very trust on your answer.
If your map is private, only you can see it. Now, if you started the map lobby and then invited him to a game, I believe he would have a copy saved locally. But if you never invited him to play, and it really was private, there's no way he should be able to access the map. Now, it used to be possible to break the security on a locked & public map, but I'm not sure if that's still possible.
Did you create any custom dependencies/mods? If you made a dependency, and then uploaded THAT publicly, he would be able to get it even if the map itself was private.