I've hired people who had their own business for a decade or more prior, so they didn't have fresh references. It's worrisome when someone's resume says they've worked for multiple companies in the last several years but they can't give you a reference, but lots of people can't for good reasons.

Also worth noting that many companies, including the one I work for, don't allow management to give references. Apparently some people have sued because they felt a poor or mediocre reference cost them a job, and some companies just don't want to take the risk when there's no benefit to them. So lots of companies are used to not being able to get references for one reason or another.

I think references are much more important when you're hiring a nanny or something like that, where a resume might not tell the story.

I'd put the dead boss as a reference. Even if they do try to call and find out what happened to him, they don't know that YOU already know that.