I searched WorldCat.org (international library catalog) and found a few possibilities:

The missing link : Eleanor Hier 1850-1918
by Cliff Thomas
Publisher: [Wales : The Author, 2008]

Found: the missing link : a genealogical study of some of the Karrs and Endsleys of Ohio and Illinois
by Helen I Pierson
Publisher: [U.S.] : The Author, 1990, ©1991.

There's also a journal the "Missing Link" published by the Cooroy-Noosa Genealogical & Historical Research Group and another journal with the same name by the San Joaquin Genealogical Society.

Another tactic -- post the names, dates, info you have and folks on the board (like myself) can search or offer advice.
It's likely that there are newspaper accounts of the crash, for example....