I had the same problem a while back when my sister borrowed my car for a day to work. When she came back, she didn't switch off the fog light. After 2-days i wanted to drive the car and when i put the key into the ignition barrel and turned, nothing happened. Not even a clicking sound. Saw the fog light switch still on so i decided to jumper the car with my mum's corolla. Took a while too. Crank it like 4times before it will start. Took it for a spin on the highway for an hour and the battery was fully charged. Reads 14v on my Blitz FATT.
Another note, my friend's car will never start after he parks it overnight. Reason is that the charging light comes on eveytime he switched the engine off hence battery power is draining when the car has no power. It was a faulty alternator in the end.