He's messing up. Sooner or later this will come back to bite him, I hope, but it's still not enough by itself to lead to the idea of a clone.
For what it is worth, Lex being more aware of what happened then he seemed to be would not lead to a conclusion of "Lex was not there". It might lead to a thought of "Lex had this taped". Actually, most likely it leads Lois to think "Lex has the DP bugged", but doesn't she already know that?
