Weed in general can make you throw up, if you have too much... but I don't think thats what happened here. Every vomit incident related to weed that I have heard was within an hour of smoking (for me it was DURING the session, and it was puking my guts out, it was little more than a dirty burp). The rest of you didn't get sick, and this was the morning after. So the weed wasn't laced and it was so far after I'm saying its not weed related. Of coarse at this point its important to note that since he is "Sick" that you may have picked up whatever he has by smoking and may become sick in a few days. Good luck with that!