Selling Drugs

I was sitting in a cheap restaurant and a man I did not know came over to me offering to sell me a drug. It sounded like Cephacol but I may not have heard it correctly. Though I had no interest in buying any drug, I feigned interest and asked him to write his phone number so I could contact him.

He then provided me with his phone number.

I assume that this is illicit. I think that possibly I should report it to the relevant agency (the FDA?; the Police Department?; the Department of Health?).

Any advice?