Except we see Slayer hanging out in Caemlyn spying on Elayne in later books (In the world of dreams version of Caemlyn, true, but since Slayer enters T'A'R in the flesh, that makes it much more likely he may have been lurking in that general location). Asmodean comes across him and recognizes him (the "You" and Slayer knifes him seeing as how he's found out. He doesn't necessarily know he actually killed Asmodean, he just knows that he's been spotted by someone, thus why he doesn't think about it later. Also, in the prologue to ToM, we see from Graendal's PoV, that apparently killing Chosen is not looked on as a good thing among the dark, so it's possible that even if Slayer knew he had killed Asmodean, he wouldn't think of it as a good thing.

Anyway, this is all irrelevant now, but after 15 years, I can't resist this one last chance to rehash the "Who Killed Asmodean" debate.

-TS