Have you ever found a database that contained records for the years 1850-1920? Did you search for your ancestor, knowing good and well that she should have a record since she lived in the area in 1865-1872? But, you did not find a record of her living there?

Did you remember to check the description of the records before you did your search? It could be that the description will show that the database does not contain records for the years 1865-1872. It may contain records for other years, but not those years.

Be careful to always check the description before using the database. It could save you quite a bit of time if there really are not records for the time period you are searching.