Just because USPS'
website talks about express 2-3 day service with reference to live animals does not mean that he did not have it shipped overnight (whether it arrived as such or not). You said yourself that you use USPS to ship overnight, so they do offer it. I highly doubt he told the postmaster that he was shipping a chameleon so he wanted 3 day shipping. I'm sure he told the postmaster he wanted overnight delivery and probably didn't tell him what he was sending.
Also, I've never had USPS update its tracking information past the initial departure until well after the package was delivered. I think there is a good chance that a day or so after the package is delivered the tracking will show a lot more information and indicate that it was not up to date.
Did you check the seller's website and see if they specify on their website what shipping method they would use? Some sellers will have a shipping or terms page on their site and will say things like "We only use overnight shipping via UPS/FedEx" or "We ship at any temperature using either hot or cold packs depending on the external temperature of the package and the time of year". If the seller specified a shipping company they didn't use or specified a cold pack when appropriate, they in effect told you it would be shipped one way and did not and you should absolutely demand a full refund for the shipping cost, regardless of the outcome (I'd still wait until the package arrives so you can know whether to demand a refund for the animal or not as well). If they refuse, post the entire story (including screen shots of their shipping policy on their website) on the BOI (
http://www.faunaclassifieds.com/forums/forumdisplay.php?f=13). If they do make such statements on their website, I would get screen shots of the shipping policy on the sellers website immediately to prevent him from changing it before you do!
Chris