Sorry for the trouble, Callista!
That haz locker keypad is unique in that it doesn't show the numerals that the player enters, making it (unintentionally) harder to know how many characters have been entered. We built it based on some real-world examples of this kind of keypad, and it tested well, but adding visual feedback of the keystrokes to that puzzle would probably have been the wiser choice.
Meanwhile, the code should have been included in the Guided Walkthrough, especially considering that some players
may not want to run up to Security and Medical in order to progress.
We'll update the walkthrough accordingly. We'll also change '5-digit' to '6-digit' (and add mention of hitting the <ENTER> key or the arrow on the keypad after entering the number -- which I suspect may have foiled some of your earlier attempts at solving the puzzle).
There are also some formatting/layout issues in that part of the walkthrough PDF which somehow sneaked past our normally vigilant QA team. We must have been doing some hard drinking or something while working on that part of the walkthrough.
I'll post an update here when the new revision is available.
Thank you for reporting this!