Chakotay is romanced by somebody he already was romanced by, but he forgot all about it. Then she’s captured and has her mind wiped so she forgets all about it, and then she leaves and he forgets all about it again. The Star Trek: Voyager Rewatch has already forgotten all about “Unforgettable.”
The problem is that, as nifty a general concept as the Ramurans’ memory-wiping pheromone is, it makes absolutely no sense in any practical way. I’ll buy that people forget about them, though it strains credulity that the pheromone would work exactly the same way on every species they encounter. But I don’t buy for a nanosecond that they also have the ability to wipe records of themselves from technology—especially not from technology they’re not familiar with. Also, how does the EMH not remember her? He doesn’t have a brain as such.
I might have been willing to buy it if Kellin had only been on board for a little while, but she was there for a week. There had to be significant evidence of her presence that would’ve been recorded by sensors in a variety of manners, and the gaps in people’s memories is something they would have investigated. I find myself reminded of TNG’s “Clues,” where they kept finding little things that showed evidence of something they didn’t remember, and they kept picking at it. Wouldn’t Voyager‘s crew do likewise?