I think it is likely that they could have died during the dam building projects of the years between 1933-1940. I have read quite a few history books from that time regarding the depression-era WPA dam blasting and building. I have seen several photos in the books that show warning posters from that era that are directed at children. The posters show dynamite and explosives and the wording was like, “DANGER! These are explosives!” And then in smaller print: “If you find these do not touch or pick up. Leave them alone and tell your parents or another adult”
In school when we studied about the Tennessee Valley Authority and other WPA dam building programs our textbooks featured the posters too. I grew up in the Midwest and the WPA provided jobs for many men here during the depression, not just dam building. My family has always spent a lot of time in state parks and you will see displays, memorials, and signs dedicated to the WPA workers. And some of my great-great uncles worked for the WPA so stories have been handed down in my family.
Sorry I meandered off topic here but I wanted to explain that I have always had an interest in history from the depression era. I have always been fascinated by dams, and my father was too,especially Hoover Dam. We visited many dams and my dad and I were able to tour Hoover Dam back when you were able to go through the behind-the-scenes tour inside the dam, which is no longer allowed.
So, back to the topic, I know from the history I have read, and heard from some of my older relatives who lived through that era, that many men died building the dams and in blasting accidents. Often the men remained unidentified, because they had traveled far to obtain work and no one knew their families or how to reach their next of kin.
It was a different era for children, too, at least in some parts of the country. Many or most children were born at home and often births weren’t registered. Families had large numbers of children and it wasn’t uncommon for one or more children to die during childhood. Accidents and misadventures were common. Sometimes a child or two would go missing and when they weren’t found it was jut assumed they had drowned, been attacked and killed by animals (in rural areas) or other accidents.
I’ve read diaries from the 1930s-1944 or so and I can’t tell you how many entries I had seen like, “The neighbors’s littlest drowned today, sorrowful but now they have one less to feed.” Or “ Brother Billy and his friend have been missing for a week now. The men searched but have given up as the children must have met demise.”
Some of the diaries would have entries like, “We found a young boy today, he is about four or five and doesn’t know his name or where is parents are so he will stay with us.”
So if this accident did happen from the 1930s-1940 I think it is possible that the families just never knew what happened, or assumed they drowned, or something else.