Redditor u/DarthMaulOpress got the ball rolling, simply asking, "What's a storyline or plot that seems to have been abandoned in NCIS?" After a friendly
spoiler warning, the original poster continued, "I think the Leon Vance is actually Tyler Owens plot/theory was worth exploring but they never did." The short post opened a floodgate of responses, with the most upvoted coming from u/ClownfishSoup, who pointed out, "You never hear about McGee's sister or his dog anymore. Or his writing career, which made him enough money to buy a Porsche and some other really nice things. Why would he give that up?" (To be fair, u/ellieacd responded, "Well, he's married and has toddler twins and a demanding career. How much time do you think he has to write?")
But that wasn't the only abandoned storyline, according to fans. "Ellie being a hot shot NSA agent with hacking skills that were almost never used," posted u/Exit-Alternative. "The women who collected Gibbs in the Merc at the end of episodes in S1," noted u/Tubbynezbit, adding, "I know it looks like one of his ex wife's, but is it ever mentioned?" Meanwhile, u/realclowntime wondered, "Jasper Shepherd ... Is he alive or not?"
But with so many seasons and stories to monitor, it's also possible that some have actually been resolved, or were never meant to be. "A lot of things on this thread are not abandoned plots but things intentionally left without an answer," wrote u/ChristmassMoose, to which u/Fickle-Negotiation76 added, "Or they have an answer and someone just missed it lol." Hmm, "NCIS" fans missing a small detail? Sounds unlikely, but stranger things have happened during the show's 19 years.
Source : https://www.looper.com/637747/you-might-not-realize-how-many-ncis-plotlines-were-abandoned/340