First, I just came back from Germany where I've seen that thing in a shop. Didn't have much time to investigate due to the kids, but guessed that it's just NFC chips with data on the headphores.
Second, I've been thinking about building a simple MP3-player for my kids for quite a while now, and (minus the obfuscation there) that's not far from what I've been thinking about doing.
Because floppies get bad sectors, the ID should be stored repeatedly on it, 4 bytes repeated to fill 1.38 MB should be redundant enough!
I suppose without ID's, one can also store the artist name and song title, and do some text search to find the MP3. Or a YouTube video.
Other thing I want (which they don't do) is the ability of resuming playback at the same position, even when putting it into a different player - that's one reason I still have some audio cassettes for the kids. No other medium I'm aware of does that kind of easy state saving. My idea there is to have the tags locked in the player in a way that gives me enough time to write the position if the user tries to remove it.