Has my cat decided it's his time?

Over the past week or so it’s been getting increasingly difficult to get my old cat to eat. He is 17 years old and has been sleeping a lot more than usual and sometimes hides. We haven’t been able to find him since yesterday afternoon and can’t find him anywhere. I am starting to get a little frantic that he may have found a place to hide and put on the big sleep, in which case it would A.) break my heart into itty bitty little pieces. and B.) make it hard to find him because he won’t come when he’s called.

Is it possible he has declared ‘game over’?
Do I have to wait for the smell in order to find him?

OK. Maybe I’m a little more than a bit frantic. I miss my lil’ buddy.