It seems that is was not a secret that Putin has a home there and that he was on holiday. The public knew this...
The Kremlin’s Choice for Chechnya - 23 August 2004
During the short visit--state news agencies reported that Putin arrived in Tsentoroi around 7:30 a.m. and was back at his Black Sea holiday residence near Sochi, where he has been for a week, by 11 a.m.--Putin’s comments were broadcast on state television. "We lost a sincere, manly, talented, and exceptionally decent person,” he said of Kadyrov. “He had no aim other than to serve his people.”
Do a Google picture search for Sochi and you will see it would not be that hard to down a plane in Sochi.