Reason for message: another user connected via Sharing

[tweaker301670]

For a bunch of reasons I don't want to get into yet I was wondering if someone could explain this to me:

If you have a desktop and laptop connected through your Airport (private network) and you close your laptop without logging out of the network and then log onto another (unprotected) network and then go to restart and you get the message that there is another user connected to you via Apple File Sharing could that be your own unterminated connection from your desktop? Or does it mean that someone went into your system? (and if that is the case is there a way of knowing what if anything was opened and/or uploaded?) TIA