This recent hint about a missing Parallels' Snapshot Manager window made me think I could cure my missing Address Book Preferences window. Somehow it had become lost, and pressing Command-, wouldn't show anything.

So after a bit digging in Adress Book's preferences, I ran this Terminal command (after quitting Address Book):

defaults write com.apple.AdressBook "NSWindow Frame Preferences" 0

This solved the problem; on next launch, the Preferences window had returned.

[robg adds: Trashing Address Book's preferences file (com.apple.AddressBook.plist) would also solve this problem, but would require much more rework to reestablish your settings. This general technique could also be used to restore any window that's gone missing due to an improper location. First find the program's preferences file in your user's Library » Preferences folder, then either open it with a text editor and search for NSWindow, or try this command in Terminal:

defaults read com.name.of.prefs | grep NSWindow

Leave off the .plist at the end of the preference file's name in the above command. The output will be a list of all window names and positions for the program in question. Find the name of the window you'd like to recover, then run the defaults write command with that window name.]