Any idea what was wrong with me?

I got home from a concert last night around midnight and around 2-3 I woke up, feeling like I was going to they up, and passed out while throwing up. I didn't have anything to drink besides water and a milkshake before the concert.  I had a salad beforehand. My friend drank some of the milkshake and is fine. I threw up probably around 15 times last night. A chemist I know thinks it was a violent reaction to a date rape drug. Anyone have anything similar happen?