Was it an Android phone? If yes, than that's one of the less known but not so rare bugs. Sometimes the WiFi network will be stuck in the "in range" state even t

Was it an Android phone? If yes, than that's one of the less known but not so rare bugs. Sometimes the WiFi network will be stuck in the "in range" state even though you are already too far away. It happened to me a few times (I could see my home network even though I was in a different country :-)). Trying to connect will fail. Switching Airplane mode on/off will fix it.