Wibbley-wobbley-timey-wimey....
Hey, if they're in 1987, that means Khan Noonien Singh is out there with his magical healing blood, which surely would have cured that old lady's kidneys. But I guess a syringe of that isn't covered by most people's insurence...
My guess is Nick Meyer brought attention to some of the time travel consequences and then made fun of them because he doesn't really give a crap about time travel consequences and he was letting us know that he doesn't take it too seriously in this film so neither should we. Just my guess though.
This
Put me down for "this," too. ^^^^^^^^
In "Tomorrow is Yesterday", Kirk finally tells Christopher the Enterprise was accidentally thrown back in time. Christopher responds that they seem to have a lot of those accidents. It's a clear reference to all the UFO sightings. So in that vein, TVH was just more "accidents" that will likely be investigated (or not) and get terrestrial explanations that don't affect the timeline.
-- The sailors were merely hallucinating. It's not like sailors have never imagined beasts and such at sea. Luckily, it was the 1980s and not the 2010s, or every sailor on that ship would've used his phone to take a picture of the Klingon ship.
-- The trash collectors saw a helicopter, it blinded them, and they ran over the trash can.
-- Kirk was either a CIA operative or a Russian spy who wanted Chekov. Either way, he had a James Bond-like laser device that melted the lock on the door. (We know they're keeping really neat stuff from us.)
-- Unless McCoy's pill left any evidence behind to be traced, what happened to the elderly woman will be chalked up to a miracle or fluke.
-- Gillian, sadly, committed suicide in the Bay, her body never found. She was distraught over the whales being released like they were.
-- Scotty feels fine with what he did because he probably left one or two critical things out of his formula for transparent aluminum, or he knows the guy will never be able to crack the matrix.
-- Chekov on the aircraft carrier is the most problematic one. The navy has Klingon technology in their hands if they want to dissect it. However, it seemed the intelligence agents were borderline competent at best, and no one took Chekov too seriously. Some crazy guy playing spaceman somehow got on board. The name doesn't check out in any intelligence base. Someone "stole" him from the hospital, which may create some interest, but when they can't find any leads, it will be "case closed." The disrupter and communicator will be stuck in a drawer somewhere, forgotten.
-- George and Gracie were lost because their tracking devices malfunctioned. For all anyone knows, they are still at sea, or they were hunted down by whalers.
-- Poor Bob was so distraught over the loss of Gillian that he bought her pickup truck and became a drifter in the CA, NV, and AZ deserts. Even though whales are not fish, he could never eat seafood again.