Question: When K is killed in the past, why is it that nobody remembers K (beyond '69 that is) but J remembers everything as it once was?
Carl Missouri
11th Jun 2012
Men in Black 3 (2012)
Answer: He meant that adult J already time traveled. In the 1960 's, K met J for the first time, when K met Detective James Edwards that was the second time, which is why he had him apply for MIB.
Chosen answer: This is answered in the movie by the character that gives J the time traveling device. The character tells J that he can still remember K because he was involved in the events. The young black child at Cape Canaveral was a young agent J. So he was there and at least passively involved.