Here are a couple of thoughts...
First, maybe the vendor is out of product and instead of coming clean and saying "I don't have any more of them in stock right now, but will get one out to you ASAP once my inventory gets re-stocked," he's trying to pass the buck on to UPS. He did actually ship it out, but maybe did so good on the group buy that he sold out and for some reason doesn't want to deal with the hassle on his own.
Second, on the UPS tracking page that one of you guys posted, it showed the product as being out for delivery. When that's posted, it's been scanned just prior to being loaded on the actual delivery truck. I used to work for a similar company and they scan the packages at pretty much every stage of the unloading/sorting/loading process that occurs at each facility. That means that it either A) got delivered to the wrong address, B) got taken off the truck for nefarious purposes, or C) was delivered and one of your neighbors or someone cruising by swiped it off your property.
If "C" were to have occurred, then it's gonna be a tricky situation unless it was a package that someone had to sign for upon delivery. I can tell you that when any of my parts that I've ordered for my cars have shipped, they generally don't require a signature and therefore get dumped on the door-step/front porch/etc. If no one is there to grab the box and bring it inside, it sits out there until someone gets home OR unless someone decides to grab it off the porch because they see it sitting there. Fortunately, I've been lucky thus far (knocking on wood).
Due to this, I can see this from both sides. You have a legitimate gripe, especially if the vendor didn't require signature upon delivery. On the other hand, if he looked at the tracking page and saw out for delivery, then it's a safe bet that he's thinking it actually made it. Either way, hopefully it gets resolved for you and hopefully vendors will read this and come to the conclusion that having signatures required for delivery would be the way to go. I don't know if it costs more, but I'd be willing to pay a couple extra bucks on shipping to have that extra peace of mind. Of course, if someone swipes it off a truck, all bets are off anyway.
