Temptation is not a sin fornication is. Fornication is a sin against oneself. The body of the believer belongs to God. He has been bought with a price and is to glorify God while in the flesh. All of this is clearly taught in this chapter.
Fornication is generally committed.
This leads one to believe that, since no one knows, or since the act was committed with a prostitute or call girl, that the sin goes unnoticed and the consequences are allayed. This is just not so. Not according to the word. God says it is fornication, sin, and those who commit such things shall not inherit the kingdom of God. It is not sex which God condemns, but it's misuse outside the marriage bond.