Right.
The only decent thing to do is to say that your dh is having an affair and that the brazen hussy hid her pants in your ds's PE bag. He confessed all and you tried to retrieve them to spare your ds embarrassment.
OR
They are your husband's. He's a cross-dresser and you've tried to keep it a secret for years.
Either way I think you need to defer blame here.
Are you sure this isn't a joke, this just seems far too comical to be true!