This is a good reminder.  I see this often in San Mateo County and throughout the SF Bay Area.  You REALLY, REALLY, REALLY need to watch your page and book numbers.

 HINTS:

1.  Verify that the index is the correct one.  Grantor-Grantee are often mixed up.

 2.  Watch page numbering and date sequences.

3.  Check for separate corporate indices, "big" name (like "Smith") separate listings, separate UCC Filing books and more.  Many things get broken out in indexes over the years and are not always shown properly on these new-fangled databases.

 4.  Be sure to understand where a digital database begins and ends and the same with each predecessor line of records from microfiche to PDF scans to microfiche to old books.  

 5.  Know your historical dates too.  Use Wikipedia to look up founding dates for your county.  In California, it's important to know whether your searching an original state county or one formed from parts of others, years later.  Know your city date of incorporation so that you know where roadway easements and abandonments are indexed:  against a city name or the unincorporated county lands that preceded it.

 6.  Ask if the older book tomes can be inspected when the film or scan is illegible.  Do they need to be ordered or can  you see them right away?  Do you keep a copy of your State Public Records Act handy for reference in acquiring the books during the posted operating hours of the county?