Isn't that the sixty-four thousand dollar question?

Ravi glowers sulkily up at Major from where he's living in his little ferret nest of Ravi clothes, wishing that he had better answers, but he didn't exactly take an elective in 'transforming back into your actual body when you've been turned into a ferret', so he's lost.

Maybe someone else will know? Maybe it's not just him. He hasn't heard about anyone else getting turned into a ferret, but he also hasn't exactly been seeking that out as a possibility, because he would've laughed and called them insane, so it's Major's best guess, right now.