Q: White Smoke From Car Hood

Hello, I went to Anaheim yesturday and my Cooling fan remained on for a duration of 6 hours, it took out the cooling Fan sensor but it was too late. As a result it drained my battery and it required a jump start. After the jump start, and when we drove in a drive thru, my engine temperature light came on, it started to blink and then it just stayed on. A few minutes later, white smoke emerged from the car Hood, I immediately pulled over and opened the hood. The smoke seemed to be coming from where the coolant resivour is located. But it was dark and I didn't get a good enough look at precisely where the smoke was coming from. I put the cooling fan sensor back in the car and the fan was able to cool the engine down, and the smoke stopped. the next morning we saw that the coolant reservoir was empty so we filled it. But when we took it for a drive the temp. sensor would come on when driving on hills. Is there another issue? I appreciate your help and answer in this regard! Thank you!

My car has 47000 miles.
My car has an automatic transmission.