I think acknowledgment should definitely been given. It's one thing to copy a recipe exactly as written, but he changed the wording to make it appear to be his own.
I can understand you being a little touchy about this right now, but you evidently explained this to him, so I think you are fine. I went through a touchy situation at one of the Facebook games I play recently as well. Someone who is not even in my "crew" (one of my game partners) was going around leaving mean "yo mama" jokes on everyone's pages. She didn't know us, and there was no reason to leave them for us. The one I got was one of the "yo mama is so ugly..." jokes and it touched a nerve for me, as my mom passed away right before Christmas in 2000. I wrote a message (polite but to the point) about the fact that some jokes may be funny in the right circumstances, but that polite people know who they should and should not tell those jokes to, and that I did not appreciate it. I noticed a few other people left similar messages for her.
I am pretty good about taking things like that in stride, but now and then I still go through my "I want my Mama" periods, and she just happened to hit during one of those.
Barbara