Callisto would just pick various items up and drop them without bothering to try to seek out their owners (and without even fully realizing that this is a thing that could be done, tbh), so she should be okay on that front! Would he try to keep her ribbon if he found it? If so, we can always go the "he removes it from the room, which makes it mysteriously disappear from his pocket and return to its original place before he can find her" route.