The latest report is that they sent out a body double in Khashoggi's clothes:
https://www.apnews.com/2e7cc6f821a14c90bec0253fe9ae9527
It seems like they expected to throw up enough distractions that their denials would hold at least among those who wanted to believe them. I think they failed to anticipate how closely Turkey was watching their consulate or that his fiancée would be waiting outside.