After I got the 'Kobold Killer' item in the tutorial quest I equipped it while I was looking at the Armor Shop wares. I then went to buy the shield as suggested but it wasn't there. It was there when I first opened the Armory though. I then exited the Armory to go back to the map, and then re-entered the Armory. The shield was there as before and I was able to purchase it. I think that equipping the new weapon while in the shop screen somehow voided the shopkeeper's inventory.
Likely you had just clicked on your Weapon slot. Selecting any particular slot will filter the inventory and, in this case, show only Weapons. The tutorial should be set up so that you're not likely to do this. I don't seem to recall getting into the situation myself; but if it's possible, well, Blue Manchu should be careful.
I'm pretty sure you're right. At the time I didn't really know how the shop worked... just glad to get into the beta and trying to be a helper. Probably useful feedback anyway? I went on to spend nearly all of yesterday plowing through the campaign... I still find the shop pretty hard to navigate. Drop down menus are really clunky.
If they're clunky, then again I say: don't use 'em! Just click on your desired slot to filter. The only cases for which this doesn't work are slots you lack (and you won't lack very many of those for long), and Treasure items.
