Unknown Aircraft

I was working as an approach controller. One day after I had transferred all traffic to the tower for landing, I went to the window to smoke a cigarette. Looking out of the window I saw anoher aircraft which was completely unknown. This aircraft was near the traffic circuit and was in a dangerous situation!!!!!
I later found out that the aircraft had lost its way and had been going from France to Poland. It hadn't communicated with any of the services because it had lost all its systems!