After unlocking PC, the typed password is available in konsole (if konsole was in forefront i.e. not in background)
Password is made visible in konsole by using up arrow on keyboard to reveal last command entered.

Version-Release number of selected component (if applicable):
Konsole version 2.6.2 on KDE 4.6.2

How reproducible:

Steps to Reproduce:
1.Konsole is in forefront.
2.Lock PC, then unlock - enter password -
3.Press up arrow on keyboard to reveal last typed command in konsole - there is the password.

Reported this to redhat/fedora bugzilla

Either I am doing something wrong or it doesn't work on Arch...

can not confirm using openSuse

Please try with other applications. Can you confirm how you have setup your screensaver, if you take any actions as part of locking or post locking (such as suspend or hibernate) or if you run any applications inside Konsole such as vim, emacs, etc which may be holding focus in some manner.

It happened to me too, only once. Recently the last three characters of my password were send by Konversation after unlocking the screen.

I could not reproduce in openSUSE.

This is possibly a race condition bug. Are you trying to type in your password prior to the lock window fully taking focus on resume for instance? (You can tell if it has focus - otherwise it won't recieve the characters you are typing in)