Car overheats and heater blows cold.

What is your question?

I was driving Friday night and on the way home my car started to steam, so I pulled over and opened the hood and coolant spewed everywhere, I put coolant in and there was a leak somewhere, but I needed to get home, so I put the coolant in, filled the reservoir, and drove home. It seemed to work, the just as I was getting home, the heater started blowing cold air, and the temperature gauge went up again. I drove to advance auto the next day to get a new thermostat and gaskets, and called my friend, who's a mechanic to see she I could get them replaced. The car has been blowing cold since, and the bottom hose remains cold while top gets hot. Is it the thermostat? What else could it be?