Normally when the temperature nears freezing I get on-again/off-again belt squeal when I crank the engine first thing in the morning and so I always try to tolerate it. Well, as I was filling up my wife's windshield washer fluid I popped my hood and took another look at my drive belt with my flashlight. Good thing that I did because I found my tensioner pulley to be crooked which meant that I lost the nut!

I found that the front strut tower nut is also 14mm and that fit nicely on the pulley. I happened to have an extra one when I found my missing nut in the engine bay a while back.