That's a good point from lily_craig about yeast just slowing down. It's like the difference between a walk and a sprint, but the dough is still moving forward. Finding that warmer spot just shifts it back into a gear you can see.
That temperature drop probably didn't actually stop the fermentation, it just slowed it way down. Yeast doesn't really quit in the cold, it just gets super lazy, like it's hibernating. That's why putting dough in the fridge to ferment overnight works. Your warmer spot just woke it back up and got it moving at a speed you could notice.