This sounds like a somewhat rare bug which we've fixed for OmniFocus 1.8, which I recognize doesn't do you any good now—but hopefully it will do you some good once you've upgraded to 1.8 (which we're planning to ship tomorrow).
Our support ninjas can help you recover your lost perspectives by email
or telephone (800-315-6664), or you can try to work through recovering them on your own by following my notes below…
The good news is your perspectives should be in your backups, as Curt suggests above. Unfortunately, OmniFocus only displays perspectives from the active database, so opening an older backup won't show you any of its perspectives. So what you'll need to do is to back up your current database, restore an older backup, save out your perspectives, restore your current backup, and load your perspectives.
First, make sure you have a current backup using File->Back Up Database.
Next, find your old backups (usually saved in Documents/OmniFocus Backups, though you can choose another location in General Preferences) and start looking for your missing perspectives by loading old backups with File->Revert to Database Backup. You can look at the contents of the Perspectives window to see whether you've found a backup with the missing perspectives.
Once you find your missing perspectives, you can use the latest sneaky peek
build of OmniFocus 1.8 to save your perspectives: in 1.8, you can save a perspective by dragging it from the Perspectives window to your desktop (or an email message or anything else which accepts a file drag).
Once you've saved the perspectives, you can restore your current backup, then add the saved perspectives back to your database by opening each of those perspective files you saved earlier.
Hope this helps, and sorry for the bug!