All that thumb pressing CPR probably didn't do squat....Not enough force and if it take an hour then you weren't doing enough anyway. It was more likely the slow warming that saved that kittens life. Despite all temptations if someone/thing is frozen DO NO INTRODUCE STRAIGHT TO HIGH HEAT like a hot water bottle or whatever. Warm them slowly with body temperature. If the warm up to quickly their blood will start flowing back to the heart faster than it can cope with, and the heart can fail.