Exactly- it was all fun and games when he was messing about with cycle helmets. Not a hint there was a problem.
Until he loses. Then all it takes is someone to suggest - well, maybe you weren't quite feeling right- and he's happy to run with it.
Now, I will hold my hands up and say 'aww, that's terrible' - if it turns out the bottle was filled with liquid mercury, weighed more than a small dog. and he actually does have delayed concussion that will put him out of action for the forseeable months.
but it's unlikely.
and I won't feel terrible at all