She did ask me what was in the box but did so in front of the rest of the family, so I settled it with a laugh and a "It's a secret". I guess I was stoking the curiosity fires there.
...although on a whim I decided to check one last time before sending my mother a long-winded email, and the batteries appear to have just fallen down. Double-check the box, it's empty, but the contents are on the lid not too far away under my bed. Not sure how that one happened, but it did. I also remember getting a pair of socks from the underwear box...I'm on a roll tonight.
I feel pretty silly. Lack of sleep made me completely and utterly paranoid.
