The primary KDE PIM address book is stored in
$HOME/.kde/share/apps/kabc.
There is a "quasi" address book based upon addresses manually used when selecting the Select (Recipient) button when composing a mail. Those address are stored in
$HOME/.kde/share/config/kmailrc, [General] Recent Addresses. You won't find those addresses in a Konqueror search because KDE is programmed to not be able to search the kmailrc file as a typical text file, although the file is strictly a text file. To see this, open Konqueror and drill to $HOME/.kde/share/config. Then find the kmailrc file and notice file type "Unknown." Then again, perhaps my system is messed up somehow.
Using grep from the command line searches through the kmailrc file just fine.