In Blish’s adaptation of “Balance of Terror,” someone (I think it was Scotty) said they could track the Romulans from their De Broglie waves as their ship moved through space. Since Blish was most likely working from an early draft script, it’s quite possible this was actually considered at one point by the writer.
ST III: Search for Spock. I think the novelization tried to assert that a combination of Chekov’s experience and pure luck let him spot the cloaked Bird of Prey, but in the movie it’s more like “Hey, what’s that distortion?”
It would, but if they’d said something about having such equipment for the mission they were prepping for before Praxis exploded, people wouldn’t have said “But wasn’t Excelsior on that mission?” an hour and a half later. And they should have had Kim Kattrall play Saavik even if Kirsty Alley wanted too much money. The Undiscovered Country’s script needed one more once-over.
As an aside, I’ve been watching the original series lately, and I have to wonder how many of those gaseous anomalies Sulu was investigating tried to possess Excelsior’s crew and/or commandeer the ship.
Toshiro Mifuni has already possessed Sulu, at least voice wise.
Aren’t they the same thing, unless you are filming The Trial? 
One can explain things better in a novel than a film.
True, but in the movie it looked like anybody could spot a cloaked ship just by looking at the main screen. In fact, a cloaked ship was downright obvious, you’d have to be blind not to see it.