There is no requirement to enter the issuing country - just to visit it. There is a line on the visa application form where applicants must indicate what the country of their entry into the Schengen zone would be. So, if the OP were going to country X but connecting at an airport in country Y that would have been in the application. And the immigration officer at the airport of country Y would have asked the OP where they were going. There are ways to establish whether the person actually went to the country that issued the visa. Not going to the issuing country at all is a misuse of visa. Some Schengen countries are rather strict about it.