It's hard to say without knowing your mapping, but there is a good chance the document property "screen_name" does not contain the term "sohail".
Try using a Match query or a Query_String.
"Term" has special meaning in ElasticSearch. A Term is the base, atomic unit of an index. Terms are generated after your text is run through an analyzer. If "screen_name" has an analyzer associated with the index, "sohail" is being modified in some capacity before being saved into the index.