While I was growing up I heard only a very few things about my family's genealogy, that it had all been "done" by my Great-grandmother and that all of her years of research had been "lost." Neither of these statements happened to be true, but I didn't know that. Until I had been accumulating genealogy for years, it never occurred to me that my Great-grandmother was not related to any of my other Great-grandparents and that she could not even have known who they were going to be and so it would be impossible for her to "do all my genealogy." It did turn out that my Great-grandmother did an awful lot of genealogy. But, of course, it also turned out to be limited to a few lines.
The second part of the early childhood fable turned out to be more problematical. Where had all of her notes and documents gone? Did some unknowing oaf of a relative simply chuck them all out to the sanitary landfill? As it turned out, a substantial number of documents, actually thousands of pages worth, were sort-of preserved by an aunt. She kept the boxes, but didn't care what was in them and didn't really want them, but the boxes ended up in her basement and she kept them there for about forty years. When she finally got tired of them, she had apparently heard I was interested in genealogy and offered the pile to my mother, who also had no interest in them but knew I might, so the boxes ended up in my living room.
The moral of this short story is simple. Seek and ye shall find, ask and it shall be given unto you. I may have found the documents much earlier had I asked my older relatives where they had gone. My aunt, who I visited many times over the years, would likely have given them to me at any time, just to get them out of her basement. There are lots of stories of unknowing family members destroying years of genealogical research out of ignorance or even malice. So, try to be there when the documents need to be transferred to a new person, make that person you.
This also brings up another issue. Family members who "own" the documents and think that no one else should see or touch them. Unfortunately, these same people seem to be the least likely to make copies or share what they have online. This can often happen when there has been an "unfortunate" incident in the family, an illegitimate child, a painful divorce, a criminal, whatever. In some of these cases, the person really does want the documents and hence, the memory, to be destroyed. This circumstance takes a great deal of diplomacy and perhaps, some cajoling.