Thanks to Cambridge Soundworks’ customer service guru, Chris Cooper, for posting a comment below and for being so helpful in our phone conversation.
I’m OK with the radio I’ve got. It seems to work just fine. And now CSW knows I’ve got it. Chris said that if they can’t fix a radio sent in for repairs, they may ship the customer a refurbished unit of the same model instead. But that wasn’t stated on this service invoice, so this may have been a genuine mixup. Chris asked me to send my “bonus” kiddie music CD back to them at their expense, which I will. In case they hear from another customer asking “where’s my Mommy and Me CD that was in the radio I sent you to repair?”