I was not using and somehow my younger brother accidentally switched off the main switch which also turned off the wifi modem at my home. Obviously my phone would lost connection to the wifi. And when I tried to reconnect to the wifi, the name of the wifi doesn't pop up anymore. I tried rebooting and full resetting my phone, nothing changed. My phone still can't detect my home's wifi but it can detect the neighbour's wifi. (I am using the GDR3 Preview for Developers)