My newly bottled beer was in <40 degree weather for 6 hours; is it ruined?

I went to the store where I'd taken a beer brewing class, bottled my beer, noted her instructions about keeping it at 70 degrees in my house, and then merrily went on my way for another five hours running errands and attending a meeting. There my beer sat in my car, and the outside temp was about 38. Inside the car was warmer, of course, but the beer still got cold.

It was only on my way home that I realized I hadn't even thought about the temp of the beer.

Is it ruined? Thankfully, it's only a one-gallon batch, but I struggle to believe that if the bottles of beer are too cold that the carbonation yeast will die; when I bake bread, it's only the high heat of the oven that kills the yeast, and lots of bread recipes explain how to let your bread raise in the refrigerator over night or longer. In fact, I keep my bread yeast in the freezer for years. Is beer yeast so different? Won't the cold temperatures yesterday simply slow it down, but not kill it?

So many questions; thanks!