Mario,

You can try the following from books online, but honestly your best
bet would be to restore to your latest backup.

David Hay

sp_attach_single_file_db
Attaches a database having only one data file to the current server.

Syntax
sp_attach_single_file_db [ @dbname = ] 'dbname'
   , [ @physname = ] 'physical_name'

Arguments
[@dbname =] 'dbname'

Is the name of the database to be attached to the server. dbname is
sysname, with a default of NULL.

[@physname =] 'phsyical_name'

Is the physical name, including path, of the database file.
physical_name is nvarchar(260), with a default of NULL.

Return Code Values
0 (success) or 1 (failure)

Result Sets
None

Remarks
When sp_attach_single_file_db attaches the database to the server, it
builds a new log file and performs additional cleanup work to remove
replication from the newly attached database.

Used sp_attach_single_file_db only on databases that were previously
detached from the server using an explicit sp_detach_db operation.

Permissions
Only members of the sysadmin and dbcreator fixed server roles can
execute this procedure.

Examples
This example detaches pubs and then attaches one file from pubs to the
current server.

EXEC sp_detach_db @dbname = 'pubs'
EXEC sp_attach_single_file_db @dbname = 'pubs',
  @physname = 'c:\Program Files\Microsoft SQL Server\MSSQL\Data
\pubs.mdf'