This is something I was looking into. Personally, I'm pretty sure it fits into the polymorphing rules in general.
Unfortunately, the information given for polymorphing doesn't seem to say anything about it either, at least as far as I could see. So, still not sure. Sorry.
Edit: Although, this thread seems to suggest that when unconscious the effect stays in place. Though, it's fairly old and not very heavy on rules quotes, so no guarantee on validity.