Simple query at App Engine Search not working

Question

I have the following data inside an index at Search API. The name and slug fields are TextFields.

Document Id         name                slug
5946158883012608    Configurations      configurations
4820258976169984    Customers           customers
6227633859723264    Sites               sites

I'm trying a lot of options of querystrings and can't get the right row.

My last tries:

• index.search('config')
• index.search('~config')
• index.search('name:~config')
• index.search('slug:~config')

If I try: index.search('customers') I receive one row. But if a remove the last s, then I receive no row.

Can someone please explain me why?

Regards,

Armando