Just because Chekov wasn’t on the bridge and we didn’t see him doesn’t mean that he wasn’t still part of the crew somewhere else on the ship. When we finally did see Chekov in Season 2, he at no point claimed to have just joined the crew.
This is how I make sense of it too. Kirk wasn’t going to put some fresh face on the bridge without serving with him for some time first.
“Who am I, Janeway? Lol!”
— James Tiberius Kirk
Picard has her beat. Fucker put a kid in the pilots seat of the flagship. A kid who hadn’t passed the entrance exam for the academy. Nepotism rears its ugly head once again.
A kid who ended up transcending spacetime, let’s not forget. Harry Kim spent seven years as an ensign before, going onto an illustrious career of never being seen again, so let’s not get ahead of ourselves…
And keep in mind that Janeway broke the Temporal Prime Directive so many times that enforcement agents had to come from the 29th century twice to stop her and one ended up going insane as a result and tried to erase her from history in several different time periods.
Edit: oh, and before you say, “she defeated the Borg,” yeah, well, not quite. Picard et al had to clean that mess up, too because she didn’t quite finish the job in her last Temporal Prime Directive violation— and who lent a hand with that? That kid he let sit at the helm and his half brother.
Either Ricardo Montalbán or Walter Koenig (I forget which of them used to tell this story) head canons it that Khan had to use the (never seen) Enterprise toilets after Ensign Chekov when he was still a lower decker, and Chekov had used the last of the toilet paper, which is why Khan burnt his face into his memory.
Khan didn’t know own how to use the three seashells?
His ass was superior
And so Khan probably would have recognized anyone he had seen on the Enterprise then, even for a second. Actual episode elapsed time can be hours or days so he likely saw most of the crew.
In case anyone is wondering, the actor says he didn’t say anything as that would reduce his screen time.
Not sure how true this is, but it’s believable.
It’s time travel
The answer is always time travel (or the Borg/Q/a combination of the three)
Pretty sure Anton Yelchin and Benedict Cumberbatch were both in Star Trek: Into Darkness
That’s another time line
Your FACE is another timeline!
let me live my dream
Your head canon is not for me to judge