This was a conscious choice made for two reasons:
(1) Two individuals (not one) disappeared on March 20, 1988 and, although it is presumed that such occured during one collective event, two separate families (not one) were consequently devastated. Accordingly, in this instance, the use of "disappearance" diminished and mitigated the ways in which the mystery of that night impacted both the Madison and Smalley families and continues to affect them two decades later.
(2) In Chapter 19 ("The Time is Now") of the book, I write:
Stacie Madison and Susan Smalley...are not just missing. They are also presumed dead...I have avoided using such terms as "death" and "murder" until now...because, knowing the Madison and Smalley families will read this book, I have done my best to be sensitive to their feelings...[but] the time for subtlety is over...[and] it is now time for someone to finally do the right thing and share what they know about the murders of Stacie Madison and Susan Smalley.
Therefore, the word "disappearances" (plural) as used in the book is intended to be synonymous with "deaths" and/or "murders."
Chapter 19 of This Night Wounds Time is available for review in its entirety at http://www.missinggirlsbook.com/Chapters.html