How could household vinegar create a salt on car carpet? I am not a chemist! My chemistry classes from my molecular biology undergrad are far behind me. But I think I created a salt, and I don't know how. Here is my mystery:

I recently got some water in my car, and wanted to prevent mold growth in my carpet mats. I brought the mats inside, vacuumed off, and completely soaked them in household vinegar. Then I placed the mats near a running dehumidifier (where the warm air comes out in the back). 

White crust appeared on the carpet. At first I thought my dehumidifier was spitting something out, but the white substance was not on any other nearby surface--only on the car carpet. Eventually as the further parts of the carpet dried, they also showed the white crust. It covers pretty much all of the carpet.

Is this, in fact, a salt? If so, what basic substance could have been in my car carpet mat that would cause this reaction? Thanks everyone!
I once had a humidifier and I ran it with tap water.  I soon noticed a build up of white dust on the carpet right in front of the humidifier.  I suspect your situation might be related to what caused my white dust.  Tap water contains salts (just like table salt), the harder the water the more salts it contains.  They are present in low concentration so you don't normally see them.  In my case, as more and more tap water evaporated it led to a visible build up of these salts.  In your case, as the water on the carpet dried, it left behind the same salts.  Maybe you really soaked your carpet with a lot of water, maybe your water is very hard, and finally, maybe salts were actually put into the carpet during their manufacturing process - and maybe washing them with vinegar (dilute acetic acid) solubilized the salts and brought them to the surface, making them visible upon drying.