Aww, I miss him too. I don't think his mom's dead, though I'm fairly certain that the reason he's not here is because she has terminal cancer and she's in bad condition. I think if his mom had died, he'd have stayed to sit shiva (spelling) and then, hopefully, come back shortly afterwards. I also think that they would have told us if she had died.
I hope he's back next year. Not to be depressing or anything, but my grandmother had terminal cancer, and she lingered for almost two and a half years...