If you didn't find it in the index, it only means that you didn't find it in the index. Looks at examples from Census, Court, printed, and various online indexes, and online Newspaper & Book sites.
Examples include:
Census Records:
Including an example of people without a last name
Age vs Year of Birth
Unindexed fields, Ancestry’s former 1930 search by birthplace
Soundex: the "G" and "H" issues
Published Family Histories
Not Indexed, Partial Index
Several "new" generations were added but the index was not updated.
Court Records
printed indexes
various online indexes
Events recorded but not indexed.
Court Records
Online Newspaper & Online Book Sites
Showing that the full text may be there while few if any of the words are indexed (correctly).
Optical Character Recognition Issues - OCR issues showing the lack of accuracy
Past Presentations:
23 October 2012 - Benedictine University - Center for Lifelong Learning Downers Grove, IL
8 November 2011 - Schaumburg Township District Library - Meeting Schaumburg, IL
24 April 2010 - Ohio Genealogical Society - Annual Conference Toledo, OH
27 February 2010 - DuPage County Genealogy Society - Annual Conference St. Charles, IL