hi smurf,
if youve never sent them a friends request, you cant unfriend them, because they arent actually on your friends list.
what you did was look at someones profile, yes? and fb has remembered it, so the name/profile keeps coming up in your searches? is that right?
i dont think youre able to remove someone who youve checked out from your search list.
if someone sees it on there and questions it, just say their name comes up because fb prompts/suggests it. which is what fb does, it 'suggests' people who you 'might know' etc.
(if you Did have them on your friends list and you unfriended them, No, they will not get a notification of your action. their friends total count will just drop by 1. and No, you also would not get a notification confirming youve unfriended someone from your friends list)