Indeed.  The problem with index errors in a computer age is that such errors can be "fixed" years later and often are and without ANY NOTICE to the public who's been searching such records for the  many years that such an error persists. 

Try this in any online county index:  RUN "SMITH", BUT RUN IT WRONG.  SWITCH THE "i" AND THE "T" TO READ "SMTIH".  Once you get a long list of hits, pull a copy of the doc.  I will be you now, that the document is correct but it is indexed wrong and that it's over 5 years old. 

Imagine all those being "fixed" today.  Every "Smith" you've ever searched in that county could have potential to create a new claim from the day of the fix, forward.

Really.  Try this.