I bet he caught you with his 3rd eye. Big buck have a habit of doing the right thing. That's how they get big!

As for did you get busted. I doubt it. He was just heading off in a diffrent direction. What I noticed about your post was there was no mention of grunting at him. Do you own a grunt? If not you might want to pick one up for just this situation. When he took a sharp left and headed to the brook I'd have given him a good grunt. Get his attention(once or twice until he acknowledges you) and then stop and let his curiosity get the best of him. If he starts away then give him another. As long as he freezes or comes it lay off it and let him come. It may have given you an opportunity at him. Just a little food for thought.

Good luck with him on you next hunts!