Bottled water contains sodium?

How much truth do you think there is, to the rumor/myth/urban legend that says water bottling companies salt their water? You know, to make you thirstier. I ask because today I rode my bike down to Walmart to buy a bubble mailer, then down to the post office to mail off Eveshka's stuff. I wasn't really thirsty when I got to Walmart but it's a warm day (73°F [22.8C for my friends in the UK and Australia] 45% humidity) with a warm breeze, so I decided to play it safe and buy a bottle of water while I was there. I drank a little bit and was IMMEDIATELY thirsty like I hadn't had liquids all day and it was over 100°F (37.8C). My throat felt dry, and there was a chemical taste and strange lubrication in my mouth. I've felt that before, when I was really dehydrated over the summer at Church camp when I was younger. Usually when I hadn't had any water in several hours in Texas summer heat.

So am I paranoid? Is it psychological? Or do you think there is something to the myth? I know when I was about 15 (1998ish) there were commercials that boasted they had no additives like sodium, which OTHER companies had. Of course these commercials never listed which competitors added sodium, but I'd heard the rumor before that Aquafina commercial. The brand of water I drank today was Deja Blue. The nutritional information label says there is 0% sodium, but I know if it's under a certain percent per volume they don't have to list it, and the serving size is like 1/3 of a 20oz bottle.

And, on top of that, when I got home I drank our filtered water from the fridge, and that nasty chemical taste and lubrication is gone, and I no longer feel like I've been wandering the desert without a canteen. So, theories? Anyone know anything for sure?

Also, Eveshka, I mailed your stuff first class with insurance, but without delivery confirmation, since it wasn't an option on the automated system.

Also this. My friend Alison posted it on her journal and my first thought was MOM NEEDS TO SEE THIS!