Why shouldn't he have beamed the captain up?
Scotty first says he wants to double-check, then
beams up Kirk! That's callous. If there's a need to double-check, this should be done before the Captain is beamed aboard. If there isn't, Scotty shouldn't waste time doing unnecessary checks.
This is what bothers me about the teaser, as it looks like Kirk's entire predicament is because Scott didn't wait for Wilson to get back with the feinberger analyzer.
I'm still impressed with that little dog extra though, he seemed pretty content wrapped up in that costume.