Bryke even said that they never descided who he was. Let's just all assume that he was "accidentally" injured fatally during Toph's labor and everyone chooses not to talk about it. That's what I imagine to cope.
I spend a good five minutes thinking that was Momo's signature or something before realizing that Toph was missing and that that was her signature. Is no one gonna comment about the sifu hotman thing or?