There are 13 total battles. Battles 11, 12, and 13 were part of an expansion pack that never got released as a stand-alone. If you are playing the Collector's CD-ROM version or the Windows 95 version, you should have those battles available, assuming you have completed all the other battles. Since you can transfer out of a Battle in progress, you may not have finished some of them. Check to make sure you actually completed every mission in every Battle. Secondary and Bonus objectives aren't required for this, so don't worry about that.
If you are playing the disk version, you don't have those Battles. If that's the case, I think you should be able find one of the CD-ROM versions I mentioned, and just copy your .plt file over and you should be able to pick up right where you left off with Battle 11.