"Well I could've sworn I found those exact ruins, but I couldn't see the guy anywhere. Too bad cause I want that armor."
From what I've read on GameFAQs and stuff the human enemies in the game and the equipment they wear level up with you (i.e. it's impossible to go to a ruin and kill a guy with daedric armor at level 4, although if a daedric weapon is something hanging around the ruin, not something you need to kill someone for, I guess you could technically get it). So you probably have to be higher level for that particular guy to appear at those ruins.
I'm still really low level - I have no time to play the game, even with me not doing homework anymore and stuff. However, I love it when I'm fighting scamps or whatever and they kill each other accidentally.