My Father Is 62 Years Of Age And Diabetic. Has A Job, But Can't Work. Lost His 401k? Please Help.

Ok so a little backstory before yapping. My dad has been working at this job for a couple years, I'd say 5 years. Recently he wasn't able to walk around very well and was in constant pain. He decided to go to the doctors and see what is going on. They prescribe him medicine and not only that but they inform him that he is diabetic and he won't be able to work until further notice. Time goes by and in the next appointment that he has they inform him that he still can't work and his blood sugar isn't doing so well. It's been about 3-4 months and it's been the same situation. Now, we, as a family are helping him decide what is best for him. I've suggested to retire that way he could still get payed. Another problem is that he had a job prior to this current one. In the other job he had. He never got his 401k money back. He never claimed it because he didn't know how to. Would he still be able to get that? Should he retire? What do we do!? It will be a huge help if anyone could give me some advice.