What’s the longest time someone you knew or know has been isolated due to addiction of substance abuse ?

A person I used to know. I never believed in judgements. I was his only friend outside of his substance-abuse circle.
He had been abandoned by his family too. For 6 years. I don't know what happened to him. Last time I met him, his health was seriously deteriorating and he was severely cachexic. I knew it was cancer. He said he's gonna get diagnosed soon. He wanted to die. I abandoned him too after a very traumatic experience.
Some people a year or so later kept calling on my number, I never picked up. He had wanted to talk to me.
He tried reaching out via a friend of mine as well. She blocked him too on my request. I think he wanted to tell me he's dying.

I think he's not even alive now.