Well, beaming up communicators was never really an option in TOS. The villains always removed those from the heroes, after which Scotty was powerless to remove them from the villains by transporting - unless somebody flipped open the device and activated it. Basically, locating or beaming up a non-activated communicator in Trek is not easier or more difficult than doing the same to a similarly sized object of some other sort, say, a pack of cigarettes. One might assume that pinpointing small things like that is much harder than pinpointing bigger things such as Vulcans or shuttlecraft.
Communicators in TOS were already said to contain advanced future technology. Perhaps a transtator would show up brightly in scanners amidst more primitive components? Then again, a transtator might be built out of perfectly ordinary materials and its sensor trace would not differ much from the transistors in a primitive radio set.
As for the episode, it's one of those "escalating plot" things where things start out innocently enough, and everything our heroes do is slightly too little, slightly too late. The audience can exclaim afterwards that everything could have been solved by doing a bit more a bit earlier, but that's not really fair, because the heroes were in no position to know that things would escalate. Suggesting overkill as the preferred approach from everything from the very start is not only detrimental to drama, it is also unrealistic...