Why is my query not using "Missing index tip"? ( SQL Server 2008 R2 )
Table creation :

CREATE TABLE dbo.table1
    (         [ID]              int primary key
            , [Data]            varchar(20)
            , [IDChamada]       varchar(50)
            , [Evento]          varchar(50)
            , [Resposta]        varchar(10)
            , [IDTarifador]     int
            , [ProximoEvento]   varchar(10))
;


You can bloat the table 

UPDATE STATISTICS dbo.Table1 WITH ROWCOUNT = 10000000, pagecount = 10000000


With your given index 

create nonclustered index nc_idChamada_evento_Rafael on dbo.table1 ( idchamada,evento) 


SQL Server is going to do a KEY LOOKUP to find other columns from your SELECT list

select [ID]
    ,[Data]
    ,[IDChamada]
    ,[Evento]
    ,[Resposta]
    ,[IDTarifador]
    ,[ProximoEvento]
from dbo.Table1
where idChamada = '18/09/15 09:08:19 010A 7E09/00'
    and evento = 'EVENTO_DE_COMPLETAMENTO'




Key Lookup is done on below columns since they are part of select query :



The index you need is 

create nonclustered index nc_idChamada_evento_KIN on dbo.table1 (
    idchamada
    ,evento
    ) include (
    [Data]
    ,[Resposta]
    ,[IDTarifador]
    ,[ProximoEvento]
    )


Above index will give you a nice seek :