If someone catches me at an odd moment, I too ask them to email me, mainly because I know I wouldn't remember all they wanted by the time I got back to my desk!!
I think the main thing is to be polite as well as assertive - be honest and say, I can't deal with your request now but email me or if you choose to, make a note and say you will get back to them. I don't think you can just listen to what they say and walk away - that would be so rude.
I too usually have a notepad on me - lost count of the number of times bossie has caught me in a corridor and asked me to do something or remind him of something - alas he is one person you cannot say "send me an email"

If I was in the ladies room and answered the phone to someone (even the boss in this case

) I would deal with it with humour. No need to get uptight - I would explain I was in the bathroom and I'll call them back. Not that I would answer the phone in there - that is the only place we run to for a bit of piece and quiet around here
