Reptile Basics wrote back to me, with apologies for the missing item.
Turns out the lack of sealed packaging on the temp gun was due to RB adding FRESH batteries to the temp gun. The clear window on the device does seem to scratch very easily (which made it look worn to me), and printed instructions with the device (rather than resorting to on-line) would have been nice, but those issues are on the mfr, not the retailer. The gun seems to be accurate and reliable, which is all I care about.
The way a business handles a transaction that doesn't go well says a lot about them.
I'll be pleased to do more business with Reptile Basics in the future.
:)