I have a friend/co-worker that is being laid off today. My question is this: when would it be appropriate to ransack her office for her REALLY cool chair and coat hanger?
This is a delicate situation. My first instinct is to tell you to grab it all the first day she's not there because you don't want someone else to get there first, but there's always a slight chance that she will drop by to pick up something she's left behind and see that you, insensitive ingrate that you are, have already benefitted from her departure.
How likely is she to stop by your office if she drops by after she's already gone? If it's not very likely that she will visit you, I say that you should go ahead and grab what you want as soon as you can, because she'll never know who did it.
If it is likely, you should take a good look at her office after she's gone. Did she get all her stuff? Does she have much reason to come around again? If it's cleaned out, wait until, oh, the second or third day she's gone and then swipe the stuff. Drape your coat over the chair in a concealing fashion for a week or two after that, and put the hanger behind your door where nobody will see it for about the same amount of time.
Also, hope that she's not one of those people who will come to visit all the time, because it could get ugly. Keep your guilty conscience in check or she'll see what you've done in your eyes.