"We found the grave and we have the organic remains," said Norman MacDonald, president of the Ossining Historical Society, the organization that oversaw the process. "The bones were not found. They have disintegrated and became part of the soil upgrade. And we found the coffin nails."
In short, no remains means no DNA testing, which means that the Old Leather Man's identity will continue to remain a mystery.
Whether it was the micro-organisms, acidic soil, an innacurate map, or something else beyond our comprehension, there is no doubt another chapter has been added to this man’s incredible tale. We now know that what remained of his physical form is truly one with the earth, while his legacy and legend continues to live on.
So although this chapter of the Old Leather Man's saga appears to be closed, as Johnson so aptly suggests, there's no doubt his story will continue. Earnest researchers as our other friend, Dan DeLuca, will now continue through archives, libraries and old attics—rather than the ground—seeking more pieces to this story.
The next thing is that what remains were exhumed were re-interred in the cemetery at a "safer" location, away from the bustling traffic of Route 9.
Maybe now, after all his wanderings, The Old Leather Man will truly be left to rest in peace.
Here's a nice wrap-up of the story from NPR.