This happened to my cat

My cat is 16 years old, he's the only cat I've ever had and I've had him since I was 4. A few weeks ago he got very sick, stopped eating and couldn't drink (he would look at every source of water and lick his mouth but make the saddest meow because he couldn't do anything else), he was covered in vomit and poop, and very cold. In a cat of his age it surely meant death. Sometimes I think he did die and come back to life. We took him to the hospital, my mom only paid for 3 days. after 2 days he was not doing any better, and she kept saying ''he's dying'' and we'd have to put him down if he wasn't miraculously better by the 3rd day (there were only a few hours left then). No one was very optimistic, not even the vet could give us any hope. He looked so sick near to death even on the 2nd day in hospital. I'm not religious but that night I said if there is anyone who can help me, I need a miracle, this is the only miracle I will need. it was to see my cat happy 1 last time, even if he was dying. the next morning he was so much better!! He was purring at the sight of us!! We got to take him home, and you could tell he was grateful. I never knew a cat could show thanks but he really did. I spent every moment i could with him, I thought he might be permanently altered, but a couple weeks later and he is 100% back to normal.

is it normal the vet made it sound like he was dying and there was nothing we could do, and that he would always be sick, yet now he is completely back to normal at the age of 16?? I am extremely grateful!! I love this cat so much