It is one of the most frustrating parts of the heirloom pursuit; realizing that there is always more you would like to know, but finding more dead ends than not. To this day, I wish I had a chance to speak to Robert Richardson and Lillian Bruce to see if there was more to know about Lillian's Yellow Heirloom; or with Archie Hook to quiz him more on Hugh's - and there are so many other examples.
It really is just genealogy, only concerning the lineage of plants and varieties instead of relatives. So much goes unexplored, unasked, or unsaid, until we realize that it is too late.