A couple of years late, but in case any other moms find this in their kid's rooms. Its Nurofen, its a british over the counter (still have to ask pharmacist) with 200 mg ibuprofen plus 12.8 mg codeine phosphate. It would be prescribed in the U.S. because of the codeine, which is a regulated opiate used for its analgesic, antitussive and antidiarrheal properties.
As to why a kid would have this pill? Codeine can be used as a recreational drug ... as in to get "high."