Well the row number can't be a seek predicate, because there's no index on the row_number.
As for the other columns, incorrect index order?
http://sqlinthewild.co.za/index.php/2009/02/06/index-columns-selectivity-and-inequality-predicates/
Also there's a chapter in Pro SQL 2012 Practices about predicates and seek predicates
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability