Well, several ounces of Febreeze later and some good all-windows-down drive time seemed to help significantly. (You should have seen the looks that got in 15 degree weather here in Portsmouth NH). Thanks all. I know, I didn't see how it's possible either. Maybe some dude flicked the thing and it landed in my vents from the topside? I never found it, but it's slowly improving. Probably a good thing this happened as it caused me to take a peek under the car and I noticed the plastic housing over the bottom of the engine was cracked and needs to be replaced.