Manufacturer warranty still holds up if the warranty is transferrable. Plus Dave Deschaine is still around and can be contacted. A friend of mine worked for him a couple years ago.
How old is the roof? It is only an issue if something goes wrong. A good inspection will give you the peace of mind either way.
Give me a call or email anytime if you have more questions.
The actual materials used (shingles) would have a manufacturers warranty. But the labor may or may not be covered under any warranty issued by the defunct roofer.