It's an unfamiliar flute.
Specifically, it's the backup flute wytchchyld gave her.
Why is she using the backup flute?
Because her usual flute, the one that cost me a shitload of money?
This is the place in the conversation where Mommy gets very, very quiet.
I have e-mailed the band teacher, asking him if he knows offhand if she left it (it has a nametag) or if he could look, should he be back in the bandroom already (school starts a week from tomorrow).
I have sent the child to go put her clean clothes away.
I am going to take a walk.