I'm fairly meticulous with my personal cards, but our group pools most of our stuff together, so differentiating between it all is tough.
I didn't exactly misplace them, but I attended my first draft tournament last Friday and had my 2 multiplayer decks stolen. I take some responisiblity for carelessly leaving them by my coat near the door, but it's rather discouraging.
I take it that the information desk wasnt able to help? I couldnt believe that that happened. That was the first time since I've been running the FNM at school that I've been aware of it happening, too.