They look like the small magnets so 37 isn't really that insane. It would be relatively easy to swallow them, I would think.
Also kids eat all sorts of crap when no one is looking. I chewed off part of a plastic cup and swallowed it. My sister swallowed a house key when my mom turned around for just a few seconds. She turned back around and the key was gone, but my sister had a smirk on her face. It's not necessarily negligence, but it does highlight the need for children to be supervised and be in a child-safe environment. Most parents do the best they can, I presume.
Yeah, these magnets are the tiny little ball magnets, not much bigger than a tic-tac a piece, if that. It would be fairly easy to swallow a bunch of them in a matter of seconds.