When you backup a db, that had data file and log file in different drives, and try restoring it to another box where any one of those drives does not exist or the path to where it is trying to restore doesnot exits, you would fail to get that restored.
What I feel is when restored to test server, and after some work is carried out again while backing up, there should not have been any thing extra done while backing up.
Also pls check if the box into which you are trying to restore this bak file, still has the path and drive existing so that it does not fail.
Or you can try to restore using the following t-sql statement.
RESTORE DATABASE TestDB
FROM DISK = 'c:\TestDB.bak'
WITH MOVE 'TestDB_Data' TO 'c:\test\TestDB.mdf',
MOVE 'TestDB_log' TO 'c:\test\TestDB.ldf'
The path may vary with that in your system. Please change that accordingly.
Hope that Helps.
Cheers!
_________________________
-Vijay G

Strive for Perfection
