I'm very sorry. I'm afraid I don't know really what it feels like, but I guess I can get a short glimpse of it. My dog, about 2 human years old, ran away about three years ago and never came back. We have no clue if he passed away or not, but even after we put up signs, there will be no way to know.
I also just recently suffered the loss of my grandfather. Hope you're all okay.
S~K