IMHO, the real thing you should be worried about here is your "friend". If s/he is stupid enough to screw around with your desktop and leave it in that condition, how do you know that they won't mention what they saw in a conversation with somebody else (not meaning any harm, of course -- just chatting) - that eventually gets around to someone at work that doesn't like what they hear?

This "friend" of yours doesn't seem too bright if they left BT3 up on your desktop at a banking institution.

I'd start by getting more intelligent friends.