Indexing methods are used to specify which characters Alchemy recognizes when indexing a database during the build process. Indexing methods are applied on a field by field basis. If a search is not returning the appropriate documents check the indexing method for the field and then access the appropriate indexing method and view the character set that is being indexed.
Note: Also review How to define Indexing Methods.
Check Indexing Methods
Make sure the character set being indexed is set-up correctly.
Check the Indexing Method associated with the Index Field
Make sure the appropriate Indexing Method was selected for this index Field.