Restore only one datafile in SQL Server 2008 from partitioned database
You can do a piecemeal restore of this data file if:


you are in full recovery mode (this is not clear in the question - I think there are many configuration options for BackupExec)
you have more than one filegroup (this is not clear in the question)
this data file is read/write and in its own filegroup (otherwise you will also need all of the other data files in this filegroup). I assume this is the case because, how else could you know that this partition exists only in this one file?
you can restore the primary filegroup and then this filegroup (in other words, the rest of the data is NOT in the primary filegroup - also not clear in the question)
you are on Enterprise Edition (again, unknown)


More details in the following articles on MSDN:


Performing Piecemeal Restores
Example: Piecemeal Restore of Only Some Filegroups (Full Recovery
Model)