The Missing Guard

[garybec]

No: HPFGUIDX 106402

Becki wonders; (and inserts the disclaimer and apology if this is an 
old topic and begs forgiveness if it has).

Where in the heck was the person that was suppose to be on guard 
duty that night that the "rescue squad" entered the MoM? 

I understand that the DE's probably got rid of the desk security 
guard, in which Harry thought was odd that there was nobody there.

But what about the OoP guard?  The one that every one always took in 
turn to guard the Department of Mysteries entrance?  Perhaps they 
were overthrown by a DE or two, but I would think that should have 
been confirmed in the book.

Any theories anyone?
Becki (who finds it challenging to read the PS and listen to the OoP 
at the same time, different intervals, of course).