I looked it up and turns out he was right: on the maps of the Russian domain - yandex.ru - Crimea is shown as a part of Russia; while on the Ukrainian - yandex.ua - it is still a part of Ukraine.
Ukraine according to maps.yandex.RU.
Ukraine according to maps.yandex.UA.
Then, I decided to check out Google Maps, since we usually expect a little more neutrality -- perhaps -- from global companies. Interestingly enough, the picture seemed as confusing there.