Hugs, CNS. I would also be really distressed if this happened, so I understand and empathize with you. Maybe it's more of an acute illness like, say, pneumonia or a kidney infection, where it's probably not life-threatening, but he doesn't know how quickly he'll be back to normal? I hope it's not something like cancer (or if it is, that it's a more easily treated kind). Maybe he's unsure of what's going on right now (or at least what a treatment plan or prognosis might be) and doesn't want to make any guarantees of when he'll be back? So that he doesn't break any promises?

I'm aware that might not help much... I do wonder if he might be willing to answer some sort of questions for you, like maybe not give any details, but explain a bit more.