No idea, really. I mean, I hope he isn't. But how can we know? My Gran always says you can't prove a negative.

I think if he got away from them (and it's clear that he did manage that much at least, because they don't have a body to show off), it's in their interest to lie about it as much as possible. It has to be ever so embarassing for the Ministry. And especially that Mrs Lestrange.